1902 Encyclopedia > Lizard

Lizard




LIZARD. The name Lizard (Lat., lacerta) originally referred only to the small European species of four-legged reptiles, but is now applied to a whole order (Lacertilia) which is represented by extremely numerous species in all temperate and tropical parts of the globe. Lizards may be described as reptiles with a more or less elongate body terminating in a tail, and with the skin either folded into scales (as in snakes) or granular or tubercular; legs are generally present—usually four, rarely two in number-—but sometimes they are reduced to rudiments or entirely hidden below the skin; the jaws are toothed, and the two mandibles firmly united in front by an osseous suture. Eyelids are generally present. The vent is a transverse slit, and not longitudinal as in Crocodilians. Other structural characteristics, especially of the skeleton, separate lizards from the other orders of reptiles; but will be better understood if described in relation to the other members of that class. See REPTILES.

At a low estimate the number of described species of lizards may be given as about one thousand seven hundred.1 They are extremely scarce north of 60° N. lat.; and in the southern hemisphere the southern point of Patagonia forms the furthest limit of their range. As we approach the tropics, the variety of forms and the number of individuals increase steadily, the most specialized and the most developed forms (the monitors and leguans) being restricted to the tropical regions where lizards abound. They have adapted themselves to almost every physical condition, except the extreme cold of high latitudes or altitudes. Those inhabiting temperate latitudes hibernate. The majority live on broken ground, rocks with or without vegetation ; others are arboreal; to a few (certain monitors) the neighbourhood of water is a necessity; whilst others are true desert animals, in colour scarcely distinguishable from their surroundings. Some, like many geckos, live near or in houses, being enabled by a peculiar apparatus of their toes to run along perpendicular and even overhanging surfaces. No lizard enters the sea, with the exception of one species, the leguan of the Galapagos (Amblyrhynchus), which feeds on sea-weed. Some, like the majority of the geckos, are nocturnal.

The motions of most lizards are executed with great but not enduring rapidity. With the exception of the chamm-aeleon, all drag their body over the ground, the limbs being wide apart, turned outwards, and relatively to the bulk of the body generally weak. But the limbs show with regard to development great variation, and an uninterrupted transition from the most perfect condition of two pairs with five separate clawed toes to their total disappearance; yet even limbless lizards retain rudiments of the osseous framework below the skin. The motions of these limb-less lizards are very similar to those of snakes, which they resemble in their elongate body passing into a long cylindrical and tapering tail.

In a great many lizards (Lacertidae, skinks, geckos) the muscles of the several vertebral segments of the tail are so loosely connected, and the axis of the vertebrae is so weak, that the tail break off with the greatest facility. The part severed retains its muscular irritability for a short time wriggling as if it were a living creature. A lizard thus mutilated does not seem to be much affected by its loss, and in a short time the part is reproduced; but, whilst the muscles and also the integuments may be perfectly regenerated, the osseous part always remains replaced by a cartilaginous rod, without vertebral segmentation. This faculty is of great advantage to the lizards endowed with it ; they are either species in which the tail has no special function, such as to assist in a particular kind of locomotion or to serve as a weapon of defence, or they are small species which lack other means of escape from their numerous enemies. The geckos are even able to throw off their tail spontaneously, and are said to do this frequently when pursued by some other animal, which is satisfied with capturing the wriggling member, whilst the owner saves its life by a rapid flight.

The majority of lizards are carnivorous, the larger feed-ing on small mammals, birds, fishes, and eggs, the smaller on insects, worms, and other invertebrates. Not a few, however, are herbivorous, as the larger leguans, and many agamas. This difference in diet is quite independent of modifications of dentition. Generally the teeth are simply conical, pointed, more rarely blunt, or notched at the top or sides. Always anchylosed with the bone, they are inserted either on the inner side of the margin of the jaws (pleurodontes), or on the edge of the bones (acrodontes). The form of the tongue exhibits many modifications which have been used for the division of the order into families, as will be seen from the systematic list given below.

All lizards are oviparous, the eggs being of an oval shape, and covered with a hard or leathery calcareous shell. The number of eggs laid is, in comparison with other reptiles small, perhaps never exceeding forty, and some, like the anolis and geckos, deposit only one or two at a time, but probably the act of oviposition is repeated in these lizards at frequent intervals. The parents do not take care of their progeny, and leave the eggs to hatch where they were deposited. In a few lizards, however, the eggs are retained in the oviduct until the embryo is fully developed; these species, then, bring forth living young, and are called ovoviviparous.

No lizard is venomous, with, perhaps, a single exception (Heloderma) to be mentioned hereafter.





The order of lizards may be divided into the following suborders and families:—

First Suborder.—Cionocrania.

Vertebrae procoelian ; an orbital ring with a temporal bar more or less complete; columella present ; parietal bone single.



Family 1. Monitoridae.—Scales of the belly oblong, quadrangular, in cross-bands, on the back and tail rhombic, very small or granular. Tongue very long, exsertile, ending in two long filaments, sheathed at the base. Head with small polygonal shields. The largest lizards, inhabiting the African, Indian, and Australian regions.

Genera: Psammosaurus, Odatria, Varanus (Monitor), Hydrosaurus.



Family 2. Tejidae.— -Scales small, granular, sometimes with larger tubercles; those of the belly oblong, quadrangular, in cross hands. Head with large symmetrical scutes. Tongue long, scaly, bifid at the end. Dentition acrodont. No fold of the skin along the sides. Tropical and subtropical America.

Genera: Tejus, Callopistes, Ameiva, Cnemidophorus, Dicrodon, Acrantus, Centropyx, Crocodilurus, Ada, Custa.



Family 3. Lacertidae.—Scutellation as in the preceding family. Tongue long, exsertile, bifid at the end, without sheath at the base. Dentition pleurodont. Old World, especially from the Europo--Asiatic, African, and Indian regions.

Genera: Lacerta, Tropidosaura, Tachydromus, Ichnotropis, Acanthodactylus, Psammodromus, Scrapteira, Eremias, Mesalina, Cabrita, Ophiops, Chondrophiops, Tracheloptychus.



Family 4. Xanthusiidae.—Distinguished from the preceding family by a broader non-exsertfle tongue. California, Central America, and Cuba.

Genera: Xanthusia, Lepidophyma, Cricosaura.



Family 5. Trachydermi.—Scales arranged in transverse rows, frequently swollen or tubercular. Tongue ending in two short points. Dentition pleurodont. No femoral pores. Central America, extending into the subtropical parts of North America.

Genera: Heloderma, Gerrhonotus.



Family 6. Zonuridae.—Scales arranged in transverse rows, quad-raugular, those of the back generally keeled; a fold of the skin runs along the side of the body, separating the upper from the lower parts. Head with large symmetrical shields. Tympanum distinct. African region; Pseudopus from the Europo-Asiatic, and Ophisaurus from the North American region.

Genera: Cordylus, Zonurus, Platysaurus, Gerrhosaurus, Pleurostrichus, Saur-ophis, Caitia, Pseudopus, Ophisaurus, Hyalosaurus.



Family 7. Chalcididae.—Scales arranged in transverse bands, quadrangular; scarcely a trace of a lateral fold in front. Head with large symmetrical shields. Tongue scaly, bifid in front. Typanum hidden. Body long, with rudimentary limbs. Tropical America.

Genera: Brachypus, Microdactylus, Chalcis, Ophiognomon, Bachia, Propus, Heterodactylus.



Family 8. Cercosauridae.—Scales rbombic or quadrangular, gene-rally arranged in transverse series. No lateral fold, or only a trace of it. Head with large symmetrical shields. Tongue scaly, bifid in front. Tympanum distinct. Body moderately elongate, with four developed limbs. Males with femoral pores. Tropical America.

Genera: Gercosaura, Pantodactylus, Chalcidolepis, Iphisa, Perodactylust Placosoma, Holaspis, Lepidosoma, Ecpleopus, Euspondylus, Cricosaura, Proctoporus, Urosaura, Emphrassotis, Lepidophyma, Loxopholis, Tratioscincus.



Family 9. Chamaesauridae.—Body slender, with rudimentary limbs. Scales arranged in transverse series, equal all round the body, provided with a sharp keel, the keels forming longitudinal ridges; no lateral fold. Typanum distinct. Tongue with a very, shallow notch in front. South Africa.

Genus: Chamaesaura.



Family 10. Gymnophthalmidae.—The entire body is covered with rounded imbricate quincuncial scales; head with symmetrical shields, No eyelids. Nostrils lateral, in a single shield. Body long, with the limbs small or rudimentary. Irregularly distributed over the tropical regions.

Genera: Gymnophthalmus, Epaphelus, Ablepharus, Blepharosteres, Cryptoblepharus, Morethia, Menetia, Miculia, Lerista, Blepharactisis.



Family 11. Pygopodidae.—Scutellation as in the preceding family, but the nostrils are situated above the upper edge of the first labial shield. No eyelids. Body long, with a pair of rudimentary hind, limbs only. Australia.

Genera: Pygopus, Delma.



Family 12. Aprasiidae.—Scutellation as in the preceding families, the nostrils in a suture between the nasal and first labial shields. -No eyelids. Limbs none. Australia.

Genus: Aprasia.



Family 13. Lialidae.—Scales imbricate, quincuncially arranged; head with imbricate scale-like shields. No eyelids. Body long-with a pair of rudimentary hind limbs only. Australia.

Genus: Lialis.



Family 14. Scincidae.—The entire body is covered with rounded imbricate scales, quincuncially arranged; head with symmetrical shields. Eyelids developed. Nostrils behind the rostral, in a separate shield, or between two or three small shields. Tongue short, with a notch in front. Ground-lizards.—This family has so wide a distribution that its range almost coincides with that of the- order generally.

The following genera are composed of numerous species, and extend over, several geographical regions: Hinulia (Indian and Australian regions), Eumeces, including Mocoa and Riopa, Lygosoma and Chelomeles (Indian and Australian regions), Plestiodon (Europo-Asiatic, North American, and Indian regions),-Mabouia and Tiliqua (Euprepes), generally distributed in the tropical and sub-tropical regions, Heteropus (Indian and Australian regions), Sphenops and Gon-gy1us (Europo-Asiatic and African regions).

Indian genera: Lipinia, Amphixestus, Lygosaurus, Caphoscincus, Ristella, Podophis, Chiamela, Senira, Brachymeles, Hagria, Tropidophorus, Norbea, Dasia, Sphenocephalus, Sepophis.

Australian genera: Hemiergis, Tetradactylus, Omolepida, Siaphos, Anoma-lopus, Rhodona, Ophioscincus, Soridia, Lioscincus, Tribolonotus, Trachydosaurus, Corucia, Cyclodus, Silubosaurus, Egernia, Tropidolepisma, Tropidoscincus, Nan-noscincus, Ophioseps.

Tropical American genera: Ophiodes, Celestus, camilia, Diploglossus, Sauresia, Panolopus.

African genera: Liolepisma, Dumerilia, Pygomeles, Eumecia, Scelotes, Thyrus, Amphiglossus, Sepsina, Sepomorphus, Herpetosaura, Sepacontias.

Europo-Asiatic genera: Scincus, Anguis, Ophiomorus, Zygnopsis, Hemipodion, Seps, Heteromeles.

North American genus: Anniella.



Family 15. Acontiidae.—Scutellation similar to that of the skinks, but the rostral shield is enlarged, cup-shaped, the nostril being in, the rostral, with a Iong slit between it and the hinder margin of the rostral. Eyes distinct, with a lower eyelid. Limbs rudimentary or absent. Africa, Madagascar, and Ceylon.

Genera: Nessia, Evesia, Acontias, Aparallactus.



Family 16. Typhlinidae.—Differing from the preceding family by having the eyes hidden under the skin. Africa, East Indian Archipelago, New Guinea.

Genera: Typhlosaurus, Feylinia, Dibamus.



Family 17. Iguanidae.— Scales of the back and sides imbricate, generally in transverse, oblique rows, those of the belly similar; head with numerous, irregular small scutes. Tongue short, scarcely, notched in front, not exsertile. Dentition pleurodont; teeth frequently compressed towards the point. Toes 5-5. The whole of this large family are found in the New World, with the exception of two genera, one (Brachylophus) inhabiting the Fiji Islands, the other (Hoplurus) Madagascar.

The genera may be divided into two groups,—one comprising arboreal forms. with compressed slender body, slender legs, and long tail, the other forms, which live on the ground, with a broader, more depressed body, stouter legs, and, shorter tail. Both groups pass into each other.

Arboreal genera: Polychrus, Urotrophus, Ecphymotes, Laemanctus, Iguana, Aloponotus, Brachylophus, Metopoceros, Trachycephalus, Oreocephalus, Cyclura, Ctenosaura, Enyaliosaurus, Basiliscus, Corythaeolus, Corythophanes, Chamaeleopsis, Ophryoessa, Ophryoessoides, Enyallius, Chamaeleolis, Xiphosurus, Dactyloa, Xiphocercus, Acantholis, Norops, Anolis, Uraniscodon, Plica.

Terrestrial genera: Tropidolepis (Sceloporus), Liodera, Liolaemus, Pygoderus, Proctotretus, Liocephalus, Helocephalus, Scartiscus, Stenocercus, Trachycyclus, Holbrookia, Uta, Aneuporus, Taraguira, Tropidurus, Microphractus, Anisophractus, Hoplurus, Hoplocercus, Strobilurus, Liosaurus, Diplolaemus, Sauro-malus, Cachryx, Uranocentron, Crotaphytus, Phymaturus, Centrura, Callisaurus, Uma, Tropidogaster, Phrynosoma.



Family 18. Agamidae.—Differing from the preceding family by their acrodont dentition. Tropical regions of the Old World and Central Asia.

Arboreal Indian genera: Draco, Sitana, Lyriocephalus, Arpephorus, Cerato-phora, Cophotis, Otocryptis, Gonyocephalus, Japalura, Dilophyrus, Orotiaris, Tiaris, Acanthosaura, Calotes, Bronchocoela, Salea, Lophocalotes, Hypselurus, Gonyocephalus, Lophura, Physignathus.

Terrestrial Australian genera: Chelosania, Ginaalia, Chlamydosaurus, Lophognathus, Diporophora, Grammatophora, Tympanocryptis, Moloch.

Terrestrial African, Indian, and Asiatic genera: Stellio, Agama, Charasia, Trapelus, Brachysaura, Phrynocephalus, Megalochilus, Centrotrachelus, Uromastyx, Liolepis, Chalarodon.



Second Suborder.—Chamaeleonoidea.



Vertebrae procoelian; a bar crossing from the parietal to the mastoid; temporal bar complete. No columella. Parietal bone single.



Family 1. Chamaeleontidae.—Body granular. Toes 5-5, formed into two grasping opposable groups. Tongue very long, worm-shaped, very extensile. Exclusively arboreal. Africa and Madagascar, one species extending into Europe and India.

Genera: Chamaeleon, Rhampholeon.



Third Suborder.—Nyctisaura.



Vertebrae amphicoelian; orbital ring and temporal bars not developed. A columella. Parietal bone paired.



Family 1. Geckotidae.—Upper parts granular, rarely with scales; lower parts covered with imbricate scales. Tongue thick, short, slightly notched in front. Eyes large, without (very rarely with) eyelids. Body depressed. Toes frequently with a more or less developed adhesive apparatus. Tropical and subtropical regions.

Genera with a wide range: Hemidactylus (Peripia), Phyllodactylus (not extending into the Indian region), Diplodactylus (Tropical America, Australia, and Africa), Thecadactylus (Tropical America and Australia), Platydactylus (Africa and Australia), Heteronota (Indian and Australian regions), Phelsuma (Indian and African regions).

Tropical American genera: Caudiverbera, Aristelliger, Sphaerodactylus, Homonota, Goniodactylus. Some of these genera go beyond the limits of the tropics southwards or northwards.

New Zealand genus : Naultinus.

Australian genera: Aedura, Rhynchoedura, Shrophura, Stenodactylopsis, Correlophus, Ceratolophus, Gehyra Nephrurus, Phyllurus.

Indian genera: Spathodactylus, Callodactylus, Ptyodactylus, Nycteridium, Pentadactylus, Gecko, Luperosaurus, Ptychozoon, Eublepharis, Geckoella, Cyrtodactylus, Gymnodactylus, Teratolepis.

African genera: Paroedura, Ebenavia, Rhoptropus, Uroplates, Theconyx, Tarentola, Pachydactylus, Psilodactylus, Pristiurus, Stenodactylus, Chondrodactylus, Geckolepis, Spatalura.

Europo-Asiatic genera: Bunopus, Ceramodactylus, Teratoscincus, Agamura. These inhabit only the southern parts of the region in Asia; representatives of some African or Indian genera (viz., Ptyodactylus, Tarentola, Gymnodactylus,

and Stenodactylus) likewise extend into this region.



This list, from which many subgenera have been excluded will give an idea of the wide distribution of the order of lizards, and of the great variety of forms which it comprises. Indeed, in both respects, it far surpasses the other orders of reptiles. The scope of the present article does not permit us to enter into further taxonomic details, but a few notes may be added on some lizards, to which special interest is attached, or of which most frequent mention made in general literature.





The first family, that of Monitoridae, comprises very large lizards, the largest exceeding a length of 6 feet. Some are terrestrial, others semi-aquatic, the former having a rounded the latter a compressed tail with a sharp, saw-like upper edge, which assists them greatly in swimming, and at the same time forms a formidable weapon with which these powerful animals can inflict deep wounds on the incautious captor. They range all over Africa, the Indian region, and Australia; their prey consists of other vertebrate animals, small mammals, birds, frogs, fishes, and eggs. The young are prettily spotted with white and black ocelli, the old ones having a plainer coloration. The Monitor of the Nile (Monitor niloticus, fig. 1) is an aquatic species, found in the neighbourhood of all large rivers of tropical Africa. The Arabs know it well under the name Waran (whence the generic name Varanus is derived), and it frequently appears also among the engravings and hieroglyphs of ancient Egypt. Some respect was and still is paid to it, as it is said to prey largely on the eggs of crocodiles. Another Monitor, the Waran el ard of the Arabs (Psammosaurus scincus), also inhabits North Africa, but is strictly terrestrial, and has a rounded tail.

Most of the European lizards with four well-developed limbs belong to the genus Lacerta. They are of small size, and insectivorous. Their tongue is deeply cleft at the end, and is frequently exserted when the animal is in a state of excitement from fear or anger. As in all the lizards of the family Lacertidae, their tail is easily broken, and as readily reproduced, the reproduced portion often assuming a monstrous or double shape, so that the animal appears to be provided with two tails. Only three species occur in Great Britain (see fig, 2). The Common Lizard (Lacerta vivipara) frequents heaths and banks in England and Scotland, and is locally met with also in Ireland; it is ovoviviparous. Much scarcer is the second species, the Sand-Lizard (Lacerta agilis), which is confined to some localities in the south of England, the New Forest and its vicinity; it does not appear to attain on English soil to the same size as on the Continent, where it abounds, growing sometimes to a length of 9 inches. Singularly, a snake (Coronella laevis), also common on the Continent, and feeding principally on this lizard, has followed it across the British Channel, apparently existing in those localities only in which the sand-lizard has settled. This lizard is oviparous. The males differ by their brighter green ground colour from the females, which are brown, spotted with black. The third British species, the Green Lizard (Lacerta viridis), does not occur in England proper; it has found a congenial home in the island of Guernsey, but is there much less developed as regards size and beauty than in the countries south of the Alps and Pyrenees. This species is larger than the two preceding; it is green, with minute blackish spots. In Germany and France one other species only (Lacerta muralis) appears; but in the south of Europe the species of Lacerta are much more numerous, the largest and finest being L. ocellata, which grows to a length of 18 or 20 inches, and is brilliantly green, ornamented with blue eye-like spots on the sides. Even the small island-rocks of the Mediterranean, sometimes only a few hundred yards in diameter, are occupied by peculiar races of lizards, which of late years have attracted much attention from the fact that they, like other reptiles, have assumed under such isolated conditions a more or less dark, almost black, coloration.

Heloderma horridum is a Mexican lizard, which in its native country has the reputation of being a most poisonous reptile. Its anterior teeth are, indeed, provided with a deep groove, as in many poisonous snakes, and the submaxillary gland is enormously developed. Sumichrast has recently proved by actual experiment on mammals the fatal effects of the bite of this lizard ; and J. Stein, a traveller in Mexico, who was bitten in the finger, suffered from symptoms similar to those resulting from the bite of a poisonous snake. It thus appears that the f ear in which it is held by the natives is not due merely to its kideous appearance, as was formerly believed. Tubercles of a dirty brown and yellow colour, with which its body is covered, give it the appearance of a leprous skin. It is about 20 inches long, and is known by the name of "Escorpion."

The Glass-Snake (Pseudopus pallasii) or Sheltopusik (Russ.) is common in Dalmatia, Hungary, southern Russia, and the western parts of Central Asia. Externally it resembles a snake, the fore limbs being entirely absent, and the hind limbs reduced to small rudiments. It attains to a length of 2 or 3 feet, and feeds on insects, worms, mice, and small birds. In captivity it becomes perfectly tame. North America is inhabited by a very similar glasssnake (Ophisaurus), and North Africa by a third (Hyalosaurus). Limbless lizards are especially common in Australia, but their scutellation is so different from that of the glass-snakes of the northern hemisphere that they are placed in distinct families, which have been noticed in the systematic list (Pygopodidae, Aprasiidae, Lialidae).

The family of skinks also includes many genera with rudimentary limbs or without any, the Slow-Worm or Blind-Worm (Anguis fragilis) being the one most generally known. It is distributed over the greater part of Europe, and rarely exceeds a length of 15 inches. Its eyes, although small, are perfectly developed and provided with eyelids. It is ovoviviparous; the young, in the first year of their life, differ considerably from the old in their coloration, the back being of a milk-white colour, with a black line down the middle. In the south of Europe it gradually disappears, and its place is taken by the similarly shaped Seps, a genus distinguished from Anguis by the presence of four very small rudiments of limbs, which have no function.

The Skink, which has given the name to the whole family, is a small lizard (Scincus officinalis) of 6 or 8 inches in length, common in and districts of North Africa and Syria. A peculiarly wedge-shaped snout, and toes provided with strong fringes, enable this animal to burrow rapidly in and under the sand of the desert. In former times large quantities of it were imported in a dry state into Europe for officinal purposes, the drug having the reputation of being efficacious in diseases of the skin and lungs; and even now it may be found in apothecaries’ shops in the south of Europe, country people regarding it as a powerful aphrodisiac for cattle.

Of the family Iguanidae we refer to three genera only:—Iguana, Anolis, and Phrynosoma. Herpetologists distinguish several species of Iguana or Leguans, which, however, do not appear to differ in their habits. They are found in the forest regions of tropical America only, in the neighbourhood of water, into which when frightened they jump from the overhanging branches of trees, to escape capture by swimming and diving. Feeding exclusively on leaves or fruits, they are themselves highly esteemed as food, and their eggs also are eagerly searched for by the natives. Iguanas grow to a length of from 2 to 5 feet, and are readily recognized by a row of long compressed and pointed scales which form a more or less high crest along the middle of the back and tail, and by a compressed and pendant dewlap at the throat. These large lizards are strictly arboreal, and of a brilliant coloration, in which green prevails.

The smallest lizards of this family belong to the genus Anolis, extremely numerous as regards species and individuals on bushes and trees of tropical America, and especially of the West Indies. They offer many points of analogy to the humming birds in their distribution, colours, and even disposition. Gosse (A Naturalist’s Sojourn in Jamaica, pp. 75 sq.) has given a vivid and faithful description of their manners. Hundreds may be seen on a bright day, disporting themselves on the trees and fences, leaping from branch to branch, fearlessly entering houses, chasing each other, or engaging in combat with some rival. Like the iguanas, they (at least the males) are provided with a large, expansible dewlap at the throat, which is brilliantly coloured, and which they display on the slightest provocation. This appendage is merely a fold of the skin, ornamental and sexual, like the wattles of the throat of a gallinaceous bird; it has no cavity in its interior, and has no communication with the mouth or with the respiratory organs ; it is supported by the posterior horns of the hyoid bone, and can be erected and spread at the will of the animal. The presence of such dewlaps in lizards is always a sign of an excitable temper. The anolis possess the power of changing their colours in a most extraordinary degree, the brilliant iridescent hues of their body passing almost in an instant into a dull sooty brown in an irritated or alarmed animal. They are much fed upon by birds and snakes, and have, like all small much-persecuted lizards, a fragile tail, easily reproduced. They bring forth only one large egg at a time, but probably breed several times during the season.

The third iguanoid, Phrynosoma, is a terrestrial form. Several species are known, inhabiting the plains of southwestern America and Mexico. Since the opening of the Pacific Railway, living specimens are frequently sent to Europe, and sold under the name of "Californian toads." Although they belong to the same family, a greater contrast than that between the nimble, slender, and longtailed Anolis and the toad-like Phrynosoma can hardly be imagined. The body is short, broad, and depressed, ending in a short tail, covered with rough tubercles or spines; the short head is armed behind with long bony spikes; the colours are a motley of brown, black, and yellow. Their defence against birds lies chiefly in their outward appearance, as, whilst they rest quiet, they are difficult to distinguish from a stone overgrown with lichen; nor have we ever found their remains in the stomach of snakes, their, spines proving a sufficient protection against these equally formidable enemies. They are said to move with rapidity in a wild state, but in confinement, especially when the animal believes itself observed, their movements are extremely sluggish and their manners uninteresting. It seems to be a common belief in California that they have the power of squirting a blood-red fluid from the corner of the eye to some distance; but nothing has been found, on anatomical examination, to establish the correctness of this assertion. They attain a length of from 6 to 8 inches.

Of the Agamidaer, which represent the iguanas in the Old World, and which have been differentiated into a still greater number of distinct generic forms, several genera deserve more than a merely nominal notice. The perhaps most highly specialized form are the Dragons (Draco), a genus of small lizards from the East Indies, more common in the archipelago than on the continent, but absent in Ceylon. The character by which they are at once recognized is the peculiar additional apparatus for locomotion, formed by the much-prolonged five or six hind ribs, which are connected by a broad expansible fold of the skin, the whole forming a subsemicircular wing on each side of the body. The snakes are the only order of vertebrates in which the ribs serve as organs of locomotion, but, whilst in that order all the ribs are charged with a function for which no other special organ exists, in the dragons only a part of the ribs are modified for the purpose of assisting four well-developed limbs. The dragons are tree-lizards; they take long flying leaps from branch to branch, supported in the air by their expanded parachutes, which are laid backwards at the sides of the animal while it is sitting or merely running. If the hind or fore limbs of a dragon were cut off, it would be helpless, and deprived of locomotion, but it could continue to move with velocity after the loss of its wings. Like the anolis, whose analogues they are in the Old World, they are provided with long highly ornamented dewlaps. These appendages are found in both sexes, one in the middle and one on each side of the throat, but they are much more developed in the mature male. The tail is very long and slender, not fragile; we have never seen a dragon in which this member was mutilated; it seems to be necessary for their peculiar locomotion, and probably its loss soon proves fatal to the animal. Cantor says that the transcendent beauty of their colours baffles description. As the lizard lies in the shade along the trunk of a tree, its colours at a distance appear as a mixture of brown and grey, and render it scarcely distinguishable from the bark. Thus it remains with no signs of life except the restless eyes watching passing insects, which, suddenly expanding its wings, it seizes with a sometimes considerable unerring leap. All the species attain a length of 7 or 8 inches, of which the tail takes at least one half. They deposit three or four eggs at a time.

Calotes is another genus of agamoids peculiar to the East Indies; it comprises numerous species well known in India by the name of "blood-suckers," a designation the origin of which cannot satisfactorily be traced. They are tree-lizards, extremely variable in their colours, which, change, not only with the season, but also at the will of the animal. The males, and in some species also the females, possess a crest of compressed scales along the back.

Of the Australian agamas no other genus is so numerously represented and widely distributed as Grammatophora, the species of which grow to a length of from 8 to 18 inches. Their scales are generally rough and spinous; but otherwise they possess no strikingly distinguishing peculiarity, unless the loose skin of their throat, which is transversely folded and capable of inflation, be regarded as such. On the other hand, two other Australian agamoids have attained some celebrity by their grotesque appearance, due to the extraordinary development of their integuments. One (fig. 5) is the Frilled Lizard (Chlamydosaurus), which is restricted to Queensland aud the north coast, and grows to a length of 2 feet, including the long tapering tail. It is provided with a frill-like fold of the skin round the neck, which, when erected, resembles a broad collar, not unlike the gigantic lace-collars of Queen Elizabeth’s time. The late Mr Krefft has made the observation that this lizard when startled, rises with the forelegs off the ground, and squats and jumps in kangaroo-fashion, thus reminding us of the peculiar locomotion ascribed to certain gigantic extinct reptiles. The other lizard is one which most appropriately has been called Moloch horridus. It is covered with large and small spine-bearing tubercles ; the head is small, and the tail short. It is sluggish in its movements, and so harmless that its armature and (to a casual observer) repulsive appearance are its sole means of defence. It grows only to a length of 10 inches, and is not uncommon in the flats of South and West Australia.

The majority of the ground-agamas, and the most common species of the plains, deserts, or rocky districts of Africa and Asia, belong to the genera Stellio and Agama. They resemble much the Grammatophora of the Australian region, their scales being mixed with larger prominent spines, which in some species are particularly developed on the tail, and disposed in whorls. Nearly all travelters in the north of Africa mention the Hardhón of the Arabs (Stellio cordylinus), which is extremely common, and has drawn upon itself the hatred of the Mohammedans by its habit of nodding its head, which they interpret as a mockery of their own movements whilst engaged in prayer. Uromastyx is one of the largest and most developed genera of ground-agamas, and likewise found in Africa and Asia. The body is uniformly covered with granular scales, whilst the short, strong tail is armed with powerful spines disposed in whorls. The Indian species (U. harderickii) feeds on herbs only; the African species probably take mixed food.

The Chamaeleons are almost peculiar to the African region, and most numerous in Madagascar, where out of the thirty-six species known not less than seventeen occur. Only one species (C. vulgaris) extends into India and Ceylon. No other member of the order of lizards shows such a degree of specialization as the chamaeleons. The tongue, eyes, limbs, tail, skin, lungs are modified in a most extraordinary manner to serve special functions in the peculiar economy of these animals. They lead an exclusively arboreal life ; each of their feet is converted into a grasping hand, by means of which, assisted by a long prehensile tail, they hold so fast to a branch on which they are sitting that they can only with difficulty be dislodged. Their movements are slow on the ground, and still more so in the water, where they are nearly helpless. As in ant-eaters, woodpeckers, or frogs, their tongue is the organ with which they catch their prey; it is exceedingly long, worm-like, with a club-shaped viscous end; they shoot it out the mouth with incredible rapidity towards insects, which remain attached to it, and are thus caught. The globular eyes are covered with a circular lid pierced by a small central hole, and are so prominent that more than one-half of the ball stands out of the head. Not only can they be moved in any direction, but each has an action independent of the other one eye may be looking forwards, whilst an object behind the animal is examined with the other. The lungs of the chamaeleons are very capacious, and are inflated when the animal is angry or frightened. The faculty of changing colour, which they have in common with many other lizards, is partly dependent on the degree in which the lungs are filled with air, and different layers of chromatophores are pressed towards the outer surface of the skin. Some species are only a few inches long, whilst others attain to a length of 18 and 20 inches. The majority are oviparous, a few ovoviviparous.

Almost all the lizards belonging to the family of Geckos may be recognized at first slight; the head is broad and depressed, the eyes large, the body depressed; the tail is thick at the base, tapering, generally somewhat deformed, as a specimen. is rarely met with in which this member is not reproduced. The limbs are stout, rather short, with at least four of the toes well developed. Geckos are found in almost every part of the globe between and near the tropics, frequenting houses, rocks, and trees; and some of the species are so numerous around and within human dwellings as to be most familiar objects to the in habitants. Many are able to run up and along the surface of a wall or of any other perpendicular object ; for this purpose the lower surface of their toes is provided with a series of movable plates or disks,1 by the aid of which they adhere to the surface over which they pass. In forest-species this apparatus is generally less developed, or entirely absent, claws being of greater use for walking up the rough bark of a tree. Geckos, with few exceptions, are nocturnal and, consequently, large-eyed animals, the pupil being generally contracted in a vertical direction, shaped like two rhombs placed with the angles towards each other. They are of small size, the largest species not exceeding 10 or 14 inches in length. They are carnivorous, destroying moths and all kinds of insects, and even the younger and weaker members of their own species. They have been seen devouring the skin which they cast off, and their own wriggling tail. They are of a fierce disposition, frequently fighting among themselves; but house-geckos readily become habituated to the presence of man; accustomed to be fed at a certain time with rice, these little lizards will punctually make their appearance, and fearlessly take the proffered food. Another peculiarity of geckos is that they, or at least some genera, are endowed with a voice. The large Gecko guttatus and G. monarchus of the East Indies utter a shrill cry, sounding like "tokee" or "tok." The common species found in houses in the south of Europe are a species of Hemidactylus (H. verruculatus) and Tarentola, the terrentola of the Italians. All geckos seem to be oviparous. (A. C. G.)


Footnotes

FOOTNOTE (page 732)

1 The two latest general works on lizards are those by Duméril and Bibron (Erpétologie. genérale, with atlas, tom. i.-ix., Paris, 1834-54, 8vo), and by J. E. Gray (Catalogue of Lizards in the Collection of the British Museum, London, 1845, 8vo). Both are now antiquated, and a new edition of either is much required.


FOOTNOTE (page 737)

1 The mechanism resembles in some the adhesive organ of Echeneis or sucking-fish, in others that of the legs of a fly.



The above article was written by Albert Günther, M.D., F.R.S., Keeper of the Zoological Department, British Museum.



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