1090 



CLASS REPTILIA. 



It is uncertain whether the remains from the American Cretaceous 

 described as Atlantochelys belong to the last-named genus. 



Family Dermochelyid/e. — This family is characterised by having 

 a carapace composed either of a median row of large and broad 

 scutes and lateral marginal rows, or of a mosaic of small irregular 

 scutes, or tessarse, traversed by longitudinal rows of larger ones. 

 The plastron varies considerably ; and the humerus, which is of the 

 flattened type of that of the Chelonidce, is distinguished from that 

 of the preceding family by the great development of its radial pro- 



Fig, ion. — Ventral aspect of the plastron and thoracic region of Protosphargis veronensis ', 

 from the Upper Cretaceous of Italy. One-fifteenth natural size. (After Capellini.) 



cess, which is situated near the middle of the shaft. The skull has 

 the temporal fossae completely roofed, as in the Chetonidce, and 

 an open tympanic ring, but has no bony floor beneath the narial 

 passage. Whereas all the members of the preceding family are of 

 moderate size, several representatives of the present one attained 

 huge dimensions. The earliest representative is the genus Eosphargis^ 

 of the London Clay, of which the one known species was originally 

 described as Chelone gigas. The skull is of the general type of that 

 of the next genus, but the carapace apparently consists only of a 

 median row of very broad and large carinated scutes, and also of 

 a row of marginals ; the structure of the plastron is not definitely 



