388 



REPTILIA— ORDER H.—CHELOIUA. 



^^. 



TU} 4 ,— POND-TOKTOISE 



(Eviys orhiiularis). 



through them — but so it is, and the student must make the best of it. If tto 

 were making animals ourselves, we Ehoukl doubtless give the members of each 

 genus a characteristic mark by which they could be recognised at a glance. 

 Foremost in this group are the true box-tortoises (Cistudo) of North America, 

 which agree with Cydemys in having a transverse hinge across the plastron, 

 the posterior moiety of which consequently forms a movable flap, capable of 

 closing the hinder aperture of the shell. As special features of the genus, may 

 be noted the hooked beak, the smooth skin covering the top of the head, the 



imperfect webbing of the toes, and the 

 extreme shortness of the tail. These 

 tortoises have a vaulted carapace, and, as 

 is usual in such cases, are mainly terres- 

 trial in their habits. From this genus 

 the depressed form of the shell serves at 

 once to distinguish the European pond- 

 tortoise (Emys orbicularis), which, with 

 an allied North American species, alone 

 represents the genus. There is no hook to 

 the beak ; the upper and lower shells are 

 united only by ligament, and the hinder 

 part of the plastron is movably articu- 

 lated by a transverse hinge. The Euro- 

 pean species not only inhabits South and 

 South-Eastern Europe, but ranges into 

 Persia and Algeria. Its shell, which grows to a little over seven inches 

 in length, is prettily speckled on the upper surface with golden flecks on a 

 blackish ground. The pond-tortoise is a carnivorous species, living upon 

 small fish, worms, and insects, and inhabiting both running and stagnant 

 waters, in which it swims and dives with great facility. It is an interesting 

 and easily-kept denizen of an aquarium. 



Of the remaining genera of the TcstiirUnidce, a very brief mention must 

 suffice. The terrapins of the genus Clemmys form a somewhat important 

 group, ranging over South Europe, North-Westem Africa, and North 

 America. In common with the four following genera, Clemmys is characterised 

 by the absence of a median ridge on the front portion of the palate of the 

 skull ; and all the species are carnivorous in their iiabits. As in all the 

 remaining genera of the family, the upper and lower shells arc firmly united 

 by suture, and there is no bony hinge in the plastron. The two species of 

 the Oriental genus Bellia may be distinguished by the stronger vertical 

 buttresses connecting the plastron with the carapace, and the small horny 

 shields covering the hinder part of the head ; the toes being completely 

 \vebbed. The more or less decided balloon-shape of the anterior vertebral 

 fdiields of the carapace is likewise a noteworthy feature of these small terra- 

 jiins. Another allied Oriental genus is typified by Dnnwuia hamiltmil, the 

 shell of which is conspicuous for its yellow markings on a black ground, and 

 the three longitudinal ridges traversing the carapace. The North American 

 terrapins of the genus Makicodemmys are also nearly allied, and have the 

 whole head covered with a smooth skin. One species frequents brackish 

 watei' ; and it is members of this genus that afford the dish so well known 

 to epicures in the United States under the name fif terrapin. 



The other members of, the family arc mainly vegetarian in their diet, and 

 differ from the foregoing by the front portion uf the broad palate bearing one 



