REPTILIA. 281 



are dilated at the base only. A single species only, H. verritciilatiis, is found 

 in Europe, the rest are principally Asiatic and Australasian. 



The three next sections are known by the enlargement of the toes at the 

 extremity only. In the first of these, Ptyodactyla, the disk is emarginate 

 in front, and provided beneath with imbricated lamellie arranged in a 

 fan-shaped manner. One species, Uroplatus jimhriatus (pi. 88, Jig. 5), 

 inhabits Madagascar. The Phyllodactyla differ from the last in the 

 absence of the inferior lamelloe. One species, P. tuberculosiis, is found in 

 California. The Sphceriodactyla have the toes dilated at the extremity into 

 an entire disk, and are entirely "without claws. The species inhabit the West 

 Indies. 



The two remaining sections are without the usual dilatation of the toes. 

 One of them, Gymnodactyla, has the simple toes unmargined and with 

 transverse striae on the inferior face. The fifth toe of the hinder feet is 

 versatile, answering the purpose of a thumb. Under this head is to be 

 ranged the curious New Holland genus PhyUurus, with a tail flattened 

 horizontally in the shape of a leaf. The concluding section, Stenodactyla, 

 embraces but a single species, Stenodactylus guttatus, a native of Egj^pt. 

 The simple cylindrical toes are indented along the edges, and are granu- 

 lar on the inferior face. The fifth toe of the hind foot is very slightly versa- 

 tile. 



Fam. 7. Varanidm. This family, interesting on account of the size of 

 some of its species, Avhich comes next to that of the crocodiles, is also 

 important for the light which it throws upon the organization of certain 

 fossil saurians. The body is greatly elongated, rounded, or cylindrical, and 

 without dorsal crests. The tail is slightly compressed, and several times 

 as long as the body. The body is provided with non-imbricated tubercles, 

 which are set in the skin, rounded, except on the belly, and arranged in 

 circular bands or rings. The belly is frequently provided with angular 

 plates. The tongue is more like that of serpents than of the other 

 saurians : it is protractile, playing in a sheath, and deeply split into two 

 forks, which are capable of separation. The teeth, which are usually 

 pointed and recurved, sometimes tubercular, are confined to the jaws, 

 where they are inserted by their roots in a common groove. Some of the 

 VaranidcB attain to a size which, among living saurians, is only exceeded by 

 the crocodiles. None, as far as known, are arboreal. They inhabit sandy 

 deserts, rocky situations, or the banks of rivers, where they feed upon insects, 

 or even the smaller vertebrate animals. The Monitor of the Nile, Varanus 

 niloticus, is said to perform essential service in devouring the eggs of the 

 crocodile. 



Of the few species of this family, but one, Heloderma horridir?n, belongs to 

 North America, where it is found in Mexico and California. None are Eu- 

 ropean : Asia, Africa, and Oceania dividing the species pretty equally. 



We shall now briefly indicate a few of the more conspicuous fossil 

 saurians, whose alliance is, to a greater or less extent, with the preceding 

 families, especially with the Varanidce. The genera Geosaurus and 

 Mosasannis were gigantic forms, each represented in the cretacean 



485 



