112 THE WASATCH AND BKLDGER FAUN.E. 



Cheloniid^. 



Postabdominal bone« distinct from each other. Chelouia Brong. 



Postabdominal bones united with each other l\v suture.. Puppigeru* Cope, 



Propleukid^ Cope.* 



Transactions of American Philo8oi>bical Society, xir, 1870, p. 235. 

 Ten costal bones; tirst two marginals united with carapace by 



suture ; shell smooth, flattened Osteopygis Cope. 



Nine costal bones; flrst two marginals united to carapace by suture; 



shell sculptured ; a high dorsal keel Feritresitts Cope. 



Nine costal bones; one marginal united with carapace by suture; 



second by costal gomphosis; shell not keeled nor sculptured. Propleura Cope, 

 t Nine costal bones; first united with carapace by suture; second 



without costal gomphosis ; shell not sculi)tured Catapleura Cope. 



t Nine costal bones ; marginals all free ; shell not sculptured Lytoloma Cope. 



TRiONTcnm^. 



a Surface of l>ones smooth. 

 Postabdominal suture digitate Axestus Cope. 



a a Surface of bones sculptured. 

 ,9 Sutures of plastron digitate. 

 A dermal flap ])n)tecting posterior legs below ; marginal bones. . . . Emyda Gray. 



A dermal flap ; no marginal bones Cyclanosteus Peters. 



No dermal flap nor marginal bones; muzzle much abbreviated Chitm Gray. 



No dermal flap nor marginal bones; muzzle elongate Trionyx Geoflfr. 



y9 /9 Suture for post-abdominal coarsely serrate. 

 Postabdominal recurved in front Plastomenus Cope. 



ClTKLYDRIDiE. 



a Bridges of plastron wide ; f caudal vertebrai. 



One row of marginal scuta; six pairs of scuta of the plastron Idiochelys Myr. 



One row of marginal scuta; scuta of i)la**tron ?not distinct IIydropelta\ Myr. 



a u Bridges of plastron very narrow. 



ft Carai)ace smooth, not sculptured. 

 Two rows of marginal scuta ; five pairs of scuta of the plastron . . Macrochelys Gray. 



Oue row of marginals ; five pairs on plastron Chelydra Schw. 



One row of marginals ; four pairs of scuta on plastron . Claudius Cope. 



;9 ji Carapace sculptured. 

 One row of marginal bones Anostira Leidy. 



Baenid^. 



Cope, Annual Report U. S. Gool. Surv. Terrs., 1872 (1873) p. 621. 

 Supramarginal scuta (lUitimeyer)and intormarginal scuta; no inter- 



humerals Platychelys Myr. 



No iiiterliuineral scnita; no sui)ramarginals Jiaena Leidy. 



luterhuiiieral S(;uta; no supramarginals .... . Polythorax\ Cope. 



'J'ala-orhrlyf norimcuntiiliiH GeolTr. liclongs to tlii» family, Vint not Valaoihclys Mjr. 



\ EanfHtrmum WnKii. {I'aliromeduiia ct Acicluhif Myr. liili' Klilinieyer) is nearly allied to BydropfUa, 



t Povsi Illy one uf lliv AJocitUe ; see Proceed. Aca<l. I'liila., Oct., 1*76. 



