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The Contemporary Review, Volume 36, September 1879

Called mud tortoises Trionyx


The

last existing reptilian order (_Chelonia_) includes, besides the land tortoises of very various dimensions, a variety of aquatic forms.

The best known of these in this country, is the marine family (_Chelonidae_), to which the edible and tortoise-shell turtles belong. The best known family in the United States and in the Continent of Europe, is the _Emydae_, to which pertain the terrapins or ordinary river tortoises. Besides these, however, there is a very small family (_Trionicidae_) of curious and exceptional forms, called mud-tortoises (_Trionyx_).

The creatures which have next to be glanced at are those familiar forms, the frogs, toads and efts, which, together with their allies, form another class,--the class _Batrachia_. These animals were long confounded with reptiles but are really widely distinct from them. They are arranged in four orders, three of which have living representatives. The creatures of the first order (the order of tailless Batrachians or _Anoura_)--frogs and toads--exist over almost all the habitable globe; and though the number of their kinds is very great, yet they are all extremely alike in organization. Many kinds (of both frogs and toads) are found to live in trees, the ends of their fingers and toes being dilated to enable them to cling to the surfaces of leaves. The most exceptional species of the whole group are the two tongueless toads, the _Pipa_ of South America and the _Daclytethra_

of Africa, the last-named kind being the lowest of all known animals provided with finger nails.

Closely related to the frogs and toads are the efts so common in our ponds. These familiar English forms are represented in other countries of the Northern Hemisphere by creatures, some of which (as we shall hereafter see) are of very great interest indeed. The whole group constitutes the second Batrachian order--the order _Urodela_.

One of the most noteworthy forms of the order is the eft _Proteus_, which inhabits the dark, subterranean caverns of Carniola and Istria. Allied to this is the _Menobranchus_ of North America and the Axolotl of Mexico. Other forms of the order are the American eft-genera _Spelerpes_ and _Amblystoma_, the _Menopoma_, and the gigantic Salamander (_Cryptobranchus_) of Japan and China, the eel-like _Amphiuma_--with its very long body and minute legs--and the two-legged _Siren_ of the United States.

The third order of Batrachians is one which contains very few species, but these are very strange, for though allied to frogs they have the appearance of snakes, or rather perhaps of worms. With long and slender bodies (marked by many transverse wrinkles), devoid of every rudiment of limb, they remind us of the before-noticed _Anguis_, _Typhlops_, and _Uropeltis_ amongst reptiles. The Batrachians in question (which belong to the genera _Caecilia_ and _Siphonops_) form the order _Ophiomorpha_.

The fourth order of Batrachians is one which has entirely passed away and become extinct. It is the order _Labyrinthodonta_, and the species which composed it were, some of them, of large size, with great heads like those of crocodiles. Others bore more or less resemblance to enlarged _Ophiomorpha_.


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