CHELONIA. 719 



The only difference between the shells of G. grandis and Mnys trijtiga is this, 

 that the shell of the former is perhaps slightly more elongated, and that each osseous 

 marginal plate is notched at the middle of its free border, and the xipMplastron 

 is somewhat larger than in Emys trijuga. The skull, while conforming to the 

 general characters of the posterior nares, palate, alveolar ledge of the maxilla, open 

 palatine foramen and broad pterygoid region of Emys, is, at the same time, a shorter 

 and broader skull destitute of a quadrato-Jugal, with a very broad frontal and nasal 

 surface. 



The shell of Geoemyda depressa presents the same characters as G. grandis, 

 only, as its specific name imphes, it is considerably depressed from above downwards. 

 The vertebral column, however, is much more flattened than in G. grandis, in which 

 the individual segments are much laterally compressed as in the small radiated land 

 tortoises, and Emys in the form of its vertebrae is intermediate between G. depressa 

 and G. grandis. The skull also of G. depressa, PL Ixxvb, figs. 1 to 6, in all its 

 characters is a miniature representation of the skull of G. grandis, although it is 

 specifically distinguishable from it in a few of its details. There is also no difference 

 between the lower jaws of Geoemyda and Emys. The bones of the feet of G. gran- 

 dis and of G. depressa have all the characters of the feet of Emys, but the bones 

 are relatively stronger, the 5th digit of the hind foot in Geoemyda and Emys 

 being provided with only one phalanx beyond the metacarpal element. The form 

 of the limb bones and of the carpal and tarsal constituents are the same in both, 

 and their respective pelves conform to one type. 



The osteological differences therefore lie only in the skulls. The examination, 

 however, of the skulls of many examples of Emydes shows that the quadrato-jugal 

 bone is frequently very feebly developed, indeed so much so that it is apt to be 

 overlooked, and if the muscular substance is roughly removed, the bone is liable 

 to be detached with it. The jugal also, in some species, is reduced to a very 

 thin rod. In both of these species, G. grandis and in G. depressa, the jugal is not 

 strong, except in very old individuals. 



In C. tricarinata the shell has the elongated character of G. grandis, but 

 the caudal is the only marginal element notched, and the vertebrae are broad, as 

 in G. depressa. The feet have much the same osteological features as in the fore- 

 going species, but the 3rd and 4th toes of the fore foot, but especially the 5th, are 

 feebler than in G. grandis, G. depressa, and in Emydes generally. The 5th toe of 

 the hind foot has the same characters as in G. grandis, G. depressa, and Emys 

 trijuga. The pelvis and other bones agree with Emys and with these two species of 



Geoemyda. 



The skulls of C. tricarinata and C. theohaldi are intermediate between the 

 skulls of G. grandis and G. depressa, and of such Emydes as E. trijuga, in which the 

 zygomatic arch is not imperfect as stated by Gray. They have the same characters 

 as regards the posterior nares, alveolar ledge, flattened area between the palatine 

 foramina, and large palatine foramen, but the last is relatively smaller than in Emys 

 trijuga. The fronto-nasal region of the skulls of C. tricarinata and C. theohatdl 



