TURTLES, TERRAPINS, AND TORTOISES 39 



Australia, although spending a considerable part of its life 

 on land, will, curiously enough, only feed under water. 

 It can be thoroughly recommended as a pet, becoming very 

 tame, and living many years under captive conditions. 



The South American Long-necked Terrapins, Hydro- 

 medusa tectifera and H. maximiliani, greatly resemble 

 Chelodina, possessing an equally long neck. They differ 

 in various osteological characters, and in the curious dis- 

 position of the dorsal shields, the nuchal being shifted back 

 behind the marginals, simulating an additional vertebral. 



In Hydraspis^ of South America, a genus composed of 

 ten thoroughly aquatic species, the shell is very much 

 flattened ; the neck is comparatively short ; the chin is 

 always provided with a pair of fleshy appendages, which, 

 however, differ much in size and shape. 



St. Hilaire's Terrati'^, Hydraspis hilarii, the largest of 

 these terrapins, attaining a shell-length of two and a half feet, 

 may be recognized by its very large club-shaped barbels. 

 Some specimens, which have been living in our gardens 

 for the past fifteen years, will, when forced to leave the 

 water, on occasions, for instance, when their tank is being 

 cleaned out, emit at intervals, for no apparent reason, a 

 loud hissing sound, which frequently develops into a shrill 

 whistle. 



Super-family Trionychoidea : — In these river turtles, 

 which constitute the single family Trionychidce, the neck 

 bends by an S-shaped curve in a vertical plane, as in the 

 Cryptodira. There are no epidermal shields, and the 

 members of this family may at once be recognized by 

 the round flat carapace, covered with soft skin, by the 



