ORDER VI 



CHELONIA 



199 



however, are too imperfectly known to admit of a precise account of their 

 structure or taxonomy. 



Propleura and Peritresius, Cope, from the Upper Cretaceous of the United 

 States, are represented by a few species, all under 1 m. in length. Desmato- 



FiG. 301. 



Thalassochelys carctta, Liun. sp. Recent ; Mediterraiiean. Ventral aspect 

 of skeleton, the plastron renioved. cor, Coracoid ; h, Hmnerus ; psc, Pre- 

 coracoid ("prescapula," Baur); r, Radius; sc, Scapula ; u, Ulna. 



Fig. 302. 



Chelone hofmanni, Gray. 

 Upper Cretaceous ; Maestricht, 

 Holland. Portion ofcarapace, i/g. 



cheli/s, Williston, from the Fort Benton Cretaceous of Kansas and Nebraska, is 

 a peculiar form with some aberrant characters, such as free nasals, stout 

 transverse processes on the cervical vertebrae, and a single articular face'on 

 the posterior cervicals. Puppigerus, Cope, occurs in the Miocene of New Jersey. 



Superfamily 2. CHELYDEOIDEA. Baur. 



No pariefo-squamusal arch ; a foramen palatmum hetween palatine and maxilla ; 

 articular faces hetween the sixth and sevenfh cervical veiiehrae not plane; niichal 

 without lower process, hut with more or less strong lateral process underlying the 

 peripherals ; one hiconvex cervical ; a complete series of inframarginals. 



Family 1. Thalasseraydidae. Rütimeyer. (Acichelyidae, Lydekker.) 



Temporal fossae of skull partially roofed. Shell cm'difm'm, mare (yr less in- 

 completely ossified, the fontaneUe in plastron persisting for a long period w thronghout 



