ORDER VI 



CHELONIA 



205 



Cover ed with epidermal shields ; plastral hones nine ; no inframarginal shields. 

 Tertiary and Recent. 



The recent genus Ghelys, Dum^ril, is made by Baur the exclusive repre- 

 sentative of this family, and separate families are established for each of the 

 following : — Hydromedusa, Wagler (Recent) ; Chelodina, Fitz. (Pleistocene and 

 Recent) ; and Bhinemys, Wagler (Eocene to Recent). In Chelodina neural 

 bones are absent, and the external surface is more or less vermiculated. 



Family 4. Rhineraydidae. Baur. 



A slender or hroad parieto-squamosal arch present ; posterior narial openings 

 bowided by maxillae, palatines, andvomer ; frontal paired ; nasals free ; premaxillae 

 distincf. Tertiary and Recent. 



Ilhinemys, Wagler (Phrynops, Wagler; Hydraspis, Bell). Eocene; India ; 

 and Recent ; South America. Emydura, Bonap. Pleistocene and Recent. 

 Flatemys, Wagler; Elseya, Gray. Recent. 



Family 5. Pelomedusidae. Cope. 



Qaadratojugal not in conneäion with parietal ; vomer rudimentary or absent. No 

 parieto-squamosal arch . and no free nasals ; frefrontals in contact. Second cervical 

 biconvex. Plastral bones eleven ; mesoplastra present. Tertiary and Recent. 



This family, as limited by Baur, includes only the recent Pelomedusa, 

 Wagler, and Sternothaerus, Bell. Cope regards the latter as the type of an 

 independent family, on account of the complete 

 mesoplastrals. The Podocnemididae difFer from 

 the preceding genera in having the quadratojugal 

 connected with the parietals. Under this head are 

 included the follow- 

 ing : — Podocnemis, 

 Wagler (Fig. 305). 

 Eocene to Recent. 

 Peltocephalus, Dum. 

 and Bibr. ; Erymno- 

 chelys, Baur. Recent. 

 Daccochelys, Lyd. Eo- 

 cene ; and perhaps 

 Taphrosphys, Cope, 



from the Upper Cre- Podocnemis expansa, Wagler. 



tappnn« of T^pw Tpr^Pv Recent; Brazil. Visceral aspect of 



taceOUS OI in ew J ersey posterior eud of plastron, showing 



and New Zealand. places for attachment of pubes and 



„, „- . ischia, a-, 2/ (after Rütimeyer). 



ihe genus Ehmo- 



chelys, Seeley (Fig. 306), from the Cambridge Greensand, known by well- 

 preserved skulls and various fragments, is of uncertain family position. 



Family 6. Plesiochelyidae. 



Skull with temporal fossae roofed. Shell usually thick, without mesoplastrals, and 

 with either a reduced or the füll number of neurals and suprapygals ; only tJie pubis 

 uniting with the xiphiplastral ; entoplastral small ; inframarginal shields at least 

 usually present. Sometimes a plastral vacuity. Phalangeals reduced. Upper Jura. 



Fig. 305. 



Rhinochelys cantubrhjieiisix, Lyd. 

 Cambridge Greensand. Skull, i/i. 

 A, Orbit; //•, Frontal; N, Nostril ; 

 na, Nasal ; pa, Parietal ; jmix, Pre- 

 maxilla ; prf, Prefrontal ; j)//, Post- 

 frontal (after Lydekker). 



