PLATTSTKRNID.'E. 



45 



Fam. 5. PLATYSTERNID^. 



Elodites Cryptoderes, part., Dmnrril Sf Bihron, Erp. Gen. ii. 1835. 

 EmydidiB, part., Grm/, Cat. Tort. 1844, and Sh. Itept. i. 18o5. 

 Clie'rsemydii, part., Strauch, Chehn. Stud. 18G:2. 

 PlatysternidiB, Gray, Suppl. Cat. Sh. liept. i. 1870. 



Nuchal plato without costiform processes. Plastral bones nine. 

 Shell covered with epidermal shields. Caudal vcrtel)r!i! mostly 

 opisthococlous. Neck completely retractile within tlie slicU. Tem- 

 poral region completely roofed over ; no parieto-sciuamosal arch. 

 Digits moderately elongate; phalanges with condyles; claws four 

 or five. 



Plastron moderately large, connected with the carapace hy liga- 

 ment ; a sei'ies of iuframarginal shields separates the plastral shields 

 from the marginals. Head very large, covered above with an un- 

 divided horny shield ; jaws very strong, hooked, without additional 

 alveolar ridges. Digits feebly webbed, all except the outer toe 

 clawed. Tail very long, subcylindrical, compressed at the end, with 

 rings of squarish shields. 



S. China, 8iam, Burma. 



The affinities of the freshwater Tortoise which is tlie only known 

 representative of this family are to a nearly equal degree with the 

 Testudinida) and with the Chelydridae. The similarity of the skulls 

 of Flatifsternxm and Macroclemm)js is very striking ; but in the 

 former the temporal roof is still more developed without, however, 

 attaining the stage of the marine Turtles, in Avhich the parietal 

 bones join the squamosals ; and the jugal presents this peculiarity, 

 unique among Chelonians, that it is completely enclosed between 

 three bones, viz. the postfrontal, the maxillary, and the quadrato- 

 jugal. The cervical vertebrae are as in a typical Emydoid ; second 

 and third opisthococlous, fourth and eighth amphieyrtous, fifth and 

 sixth precocious, seventh amphicoelous ; there are three ginglymoid 

 articulations (v., vi., vii.). The symphysial branches of the pubis 

 and ischium arc parallel, but connected only by ligament. The 

 three anterior caudal vertebrae are procoelous, the next ami)hicoelous, 

 then fellow a series of nineteen opisthoccelous ; the last ten are 

 again procoelous. The neural plates form a complete series ; they 

 are, with the exception of the first, broader than long and hexa- 

 gonal. Two pygals are present, in addition to the azygos marginal. 

 The plastron is separated from the carapace by ligament, and 



