242 TRIONTCHID^, 



1. TRIONYX. 



Eniys, part., Diim6r. Zool. Anal. p. 76 (1806). 



Trionyx, part., Geofr. Ann. Mus. xiv. p. 1 (1809) ; Fitzing.N. Class. 



Hcpt. p. 7 (182r.) ; Grmj, Syn. Rept. p. 45 (1831) ; Strctuch, Chclon. 



Stud. p. 50 (18G2). 

 Aspidonectes, Wayler, Syst. AmpJi. p. 134 (1830) ; Agassiz, Contr. 



N. If. U. S. i. p. 403 (1857). 

 Gyranopus, part., Dum. ^- Bibr. ii. p. 472 (1835). 

 Platypeltis, FUziny. Ann. Wien. Muft. i. p. 127 (1835); Agassiz, I.e. 



p. 400; Gray, Supjjl. Cat. Sh. liejjt. i. p. 107 (1870), ««(/ Pi-oc. 



Zool. Soc. 1S73, p. 58. 

 Pelodiscus, Fitzing. I. c. 



Auiyda, Fitztnrj. I. c. ; Ayassiz, I. c. p. 398 ; Gray, II. cc. pp. 95, 62. 

 Tyrse, Gray, Cat. Tort. p. 47 (1844), andU. cc. pp. 107, 62. 

 Trionyx, Gray, Cat. Tort. p. 49, ayjd Sh. Ilept. i. p. 04 (1855) ; 



Gunth. Rejit. Brit. Ind. p. 46 (1804) ; Gray, Suppl. Cat. Sh. Rejd. 



i. p. 97, and Proc. Zool. Soc. 1873, p. 47. 

 Dogania, Gray, II. cc. pp. 49, 69, 105, 56. 

 Eafetus, Gray, Proc. Zool. Soc. 1864, p. 81, and Suppl. Cat, Sh. 



Rcpt. i. p. 103, ayid Proc. Zool. Soc. 1873, p. 64. 

 Aspilus, Gray, II. cc. pp. 83, 101, 65. 

 Potamoclielvgi, part., Gray, Proc. Zool. Soc. 1864, p. 85, and Sup])l. 



Cat. Sh. Repf. i. p. 104. 

 Landemaiiia, Gray, Proc. Zool. Soc. 1869, p. 215, and Suppl. Cat. 



Sh. Repf. i. p. 9*6, and Proc. Zool. Soc. 1873, p. 53, 

 Fordia, Gray, II. cc. pp. 219, 96, 43. 

 Callinia, Gray, II. cc. pp. 221, 108, GO. 



Sarbieria, Gray, Proc. Zool. Soc. 1869, p. 220, and Suppl. p. 100. 

 Nilssonia, Gray, Ann. ^- Mag. N. H. (4) x. p. 332 (1872), and Proc. 



Zool. Soc. 1873, p. 45. 

 Isola, Gray, Proc. Zool. Soc. 1873, p. 51. 

 Ida, Gray, I. c. p. 55. 



Oscaria, ^Gray, Ann. Sf Mag. N. IT. (4) xii. p. 157 (1873). 

 Yuen, Heude, Mem. Hist. Nat. Emp. Chin. i. p. 18 (1880). 

 P.silognatlins, Heude, I. c. p. 24. 

 Temuognathus, Heude, I. c. p. 25. 

 Gomphopelta, Heude, L c. p. 27. 

 Coelognathus, Heude, I. c. p. 29. 

 Tortistermim, Heude, I. c. p. 31. 

 Ceramopelta, Heude, I. c. p. 33. 

 Coptopelta, Heude, I. c. p. 34. 

 Cinctisternum, Heude, I. c. p. 36. 



Outer extremities of the nuchal plate overlying the second dorsal 

 rib; neural plates well developed. Limbs completely exposed. 

 Hyoplastron distinct from hypoplastron ; not more than five plastral 

 callosities. Bony choana) between the orbits ; jaws strong : post- 

 orbital arch narrower than the diameter of the orbit ; pterygoids, 

 posterior border free, withoiit ascending process. 



Africa, Asia, North America. 



The fact that the width and shape of the alveolar surfaces of 

 the jaws may vary considerably in Turtles of this genus which, in 

 all other respects, must be regarded as closely related or even 

 identical, was first pointed out by Agassiz, who seized upon the 



