Lizard

2. Uroplatidae.—A single genus in Madagascar, the best known species being Uroplates fimbriatus; this is a gecko-like creature with large eyes covered by a transparent membrane and with ad hesive lamellae on the digits. The body is depressed and its lateral edges are produced into a fimbriated fold of skin which also borders the edges of the limbs; the tail is much flattened, leaf-like and with its outline broken by numerous indentations and the colouring so closely imitates a patch of lichen that when the animal is at rest on a tree trunk the broken outline and cryp tic colouring render it very inconspicuous.

3. Xantusiidae.—A small Central and Western American family with well developed limbs, no adhesive lamellae on the fingers or toes but without movable eyelids. Xantusia occurs in the desert regions of California and Nevada, Lepidophyma in Central America and Cricosaura in Cuba.

4. Dibamidae.—A single genus of burrowing forms in the Ma layan region from New Guinea to S. Annam and the Nicobar Islands. Limbs are entirely absent in females but the hind ones persist in males as a pair of stylets which are probably used as claspers. The body is serpentiform, covered with small imbricat ing scales and the eyes are entirely covered by the skin.

5. Feyliniidae.—Another small family of degenerate, burrowing forms without any external rudiments of limbs and with the eyes completely covered over by the skin; Typhlosaurus in Madagas car and Feylinia in West and South Africa.

6. Anelytropsidae.—A single species only is known of this family, Anelytropsis papillosus, a burrowing creature found in the humus of the forests of Mexico ; in all outward respects it resembles the members of the preceding family in which it was formerly included.

7. Scincidae.—This is one of the largest families of lizards and is cosmopolitan in its distribution ; in America it is comparatively poorly represented but the tropical parts of the Old World possess a bewildering variety of forms. All have hard, overlapping scales beneath each of which is a bony plate embedded in the skin; limbs may be well-developed with five fingers and toes, or com pletely absent and every intermediate condition can be found; in some the fore-limbs show greater reduction than the hinder pair but in others the converse is true and limb-reduction appears to have taken place, not once, but many times within the family. The largest species is the Blue Tongued Lizard (Tiliqua scin coides) of Australia, a heavy-bodied creature which may reach a length of two feet and which has relatively short pentadactyle limbs ; other well known Australian forms are the Stump-tailed Skink (Trachysaurus rugosus), with large rough scales and a short, broad tail and Egernia stokesii also with a short tail whose scales are enlarged to form thorn-like spines. Lygosoma is cir

cumtropical in its distribution and its numerous species show every stage of limb reduction ; this reduction is correlated with burrowing or cryptozoic habits and occurs in widely separated groups of species in different localities. Though most skinks are ovoviviparous a few species in this genus lay eggs, among them the widespread Blue-tailed Skink (L. cyanurum) which occurs in large numbers on almost every Pacific Island from Tahiti to New Guinea; on the other hand, one or two South Australian Lygosomas are known to be truly viviparous. Another modifica tion, of which gradational stages can be traced, is the development of a transparent disc in the lower eyelid, apparently in correlation with life in desert or sandy regions; commencing as a few en larged semi-transparent scales on the lower eyelid, in the more advanced forms almost the whole eyelid has lost its scaly charac ter and become quite transparent. The same modification has also occurred in other genera and reaches its highest development in such forms as Ablepharus and Ophiopsiseps, where the trans parent lower lid is fused with the edge of the upper and thus superficially resembles the transparent eye-covering of the geck oes and their allies. Mabuya, another large circumtropical genus, closely resembles Lygosoma and has undergone almost all the same modifications; the limbs are not, however, completely lost and no species are as yet known to be viviparous. The Skink, the species which has given its name to the whole family, is a small N. African and Syrian desert-dwelling form, Scincus officinalis, with a peculiar wedge-shaped head, small eyes and very short limbs; the edges of the fingers and toes have a fringe of short, broad scales which render the hands and feet paddle-like and by means of these, assisted by the wedge-shaped head, the animal can dive into, and literally swim through, loose sand. Clialcides a genus of southern Europe, N. Africa and western Asia shows again various stages of limb reduction and the development of a transparent disc in the lower eyelid and one species, C. tridacty lus is viviparous.