THE LAND TORTOISES AND TERRAPINS 2421 



other species, on the contrary, seem to be mainly aquatic in their habits; the den- 

 tated hinged tortoise, which is fairly common in Guinea, being stated to spend a 

 large portion of its time in the water, where one specimen remained for upward 

 of a month. According to Falkenstein, it is found in rivers, even close to the 

 sea, from whence it emerges to lay its eggs on their banks. In spite of its club- 

 like feet, it dives and swims with facility; captive examples descending to the bottom 

 of a deep vessel in which they were kept. On land, its motions are,* however, 

 slow and deliberate in the extreme, and have been compared to those of the 

 minute hand of a clock. Its food is of a vegetable nature; one captive specimen 

 displaying great partiality for cherries. By the inhabitants of Guinea these tortoises 

 are eagerly sought after as food, and are thus difficult to obtain by Europeans. 



The last member of this section of the family is the spider tortoise 

 ?1 ^ (Pyxis arachnoides) of Madagascar, which is the sole representative of 



a genus characterized by the presence of a transverse hinge across the 

 front of the plastron, by which means the anterior lobe of the latter can be bent 

 upward so as to close the front of the shell. In having the neural bones of the 

 carapace alternately octagonal and tetragonal, this species approaches the true tor- 

 toises nearer than do the hinged tortoises. In length the shell is only just over 

 four inches; its coloration is yellow, with radiating black bands from the centres of 

 the shields of the back. 



The whole of the tortoises hitherto described are collectively charac- 

 terized by the absence of all trace of webbing in the toes, by the 

 Terrapins 



presence of not more than two joints, or phalanges in each toe, by the 

 metacarpal bones of the fore-foot being but slightly, if at all, longer than wide, and 

 also by the majority of the bony neural plates of the carapace being hexagonal, 

 with their shorter lateral surfaces posteriorly placed, or alternately octagonal and 

 tetragonal. On the other hand, in the remaining members of the family, the digits 

 are usually furnished with webs, or at least a rudiment thereof, while the middle 

 toe of each foot has three joints, and the metacarpal bones are elongated. We have 

 first to deal with a small group, mainly confined to the Oriental region, which both 

 in structure and habits tends to connect this section of the family with the preced- 

 ing one. These forms, as shown in the right-hand figure of the illustration on p. 

 2 399. agree with the hinged tortoises in that most of the hexagonal neural plates of 

 the carapace have the shorter of the two lateral surfaces placed posteriorly and the 

 longer anteriorly. Moreover, if the horny shields from the plastron be removed, it 

 will be found that the entoplastral, or median unpaired bone of that part of the 

 skeleton, is crossed by the groove marking the boundary between the humeral and 

 pectoral shields. 



The spinose land terrapin (Geoemyda spinosa} may be taken as a 



well-known example of the first genus, characterized by the absence 



of a hinge in the plastron and of a bony temporal arch on the sides of 



the skull. The three species of this genus are large-sized tortoises, confined to 



Burma and the Malayan region; the spinose land terrapin having a shell of eight 



inches in length, while that of the great land terrapin (G. grandis) from Burma 



and Siam measures upward of sixteen inches. In the former of these two species 



