no8 



CLASS REPTILIA. 



In Chrysemys itself the sulcus between the humeral and pectoral 

 shields of the plastron is situated entirely on the hyoplastral, as in 

 fig. i o 1 6 ; and from the presence of this feature, it is probable 

 that the so-called Emys testudiniformis and E. bicarinata, of the 



London Clay, should be re- 

 ferred to this genus. In the 

 existing genus Ocadia, from 

 China, and also in the Palse- 

 arctic and North American 

 Clemmys, the humeropectoral 

 sulcus is placed somewhat 

 more anteriorly, and conse- 

 quently cuts the entoplastral 

 bone. A similar feature is 

 frequently found in the so- 

 called Emys crassa {hordwel- 

 /iensis), of the Upper Eocene 

 of Hampshire ; and it ap- 

 pears that this form should 

 be referred to the genus 

 Palczochelys, of the German 

 Miocene, from which Ocadia 

 is probably not separable. 

 Emys wyomingensis, of the 

 Upper Eocene of North 

 America, appears to be re- 

 ferable to the same genus. 

 Ocadia, it may be observed, 

 agrees with the herbivorous 

 Batagurs in the presence of ridges on the palate ; but these ridges 

 are absent in C/emmys and the undermentioned forms, which are 

 purely carnivorous. 



These forms may be divided into two groups, according as to 

 whether the plastron is united to the carapace by suture, or simply 

 by ligament. In the former series Clemmys is represented in the 

 Pliocene of Algeria by a species closely allied to the existing C. 

 leprosa of that region. The characteristic Oriental genera Damonia 

 and Bellia are represented in the Pliocene Siwaliks of India ; the 

 fossil Damonia being apparently inseparable from the living D. 

 Hamiltoni. In the second series, where there is a more or less 

 complete transverse hinge in the plastron at the junction of the 

 hyo- and hypoplastrals, and the buttresses of the carapace may be 

 wanting, we find remains of the existing Emys orbicularis (E. lu- 

 traria or Lutremys), commonly known as the European Pond-tor- 

 toise, in the Pleistocene of England and the Continent. Cistudo, 



Fig. 1017. — Carapace of Hardella Thurgi; India. 

 nu, Nuchal bone ; ui-n8, Neural do. ; spy, Supra- 

 pygal do. ; py, Pygal do. ; ci-c8, Costal do. ; 

 7ni-7niz, Marginal do. Reduced. 



