IJaur.] -"^1-^ [May ft, 



Emydura Bonaparte, 1836.* 



EUeya {QvAy part, 18(57) Boulenger, 18S9. 



These I place all in one family which I call Rhinemydidm. 



Rhinemydidm. 



A slender or broad parieto-squamos%l arch. Posterior nasal openings 

 bounded by maxillary, palate and vomer ; frontal double ; nasals free ; pre- 

 maxillary double. 



The ChelyicUe, ChelodiuidiB, Rhiaemydidae and Hydromedusidoe form 

 one natural group of the Pleurodira, which has been already established 

 by me in 1887,f but without proper name. I propose to call it 



Chkltoidea. X 



Fifth and eighth cervical vertebrce biconvex ; no m,esoplastron ; no quad- 

 ratojugal; vomer present and complete. 



The second group of the Pleurodira, which contains the families Pelo- 

 medusidfe and Podocnemididae, may be called 



Pelomedusoidea. 



Second cervical biconvex ; a mesoplastron ; quidratojugal present ; vomer 

 rudimentary or absent. 



PelomedusidcB. 



Quadratojugal without connection with parietals. 

 Pdomedusa Wagl., Sternothmrus (Bell) Gra3\ 



PodocnemididcB. 



Quadratojugal in connection with parietals. 

 Podocnemis Wagler; Pcltocephalus, Dum. and Bibr. 

 Erymnochelys Baur.g 



Intermediate Extinct Family Bothremydidm.} 



Vomer well developed ; no free nasal bones ; dentaries coossified ; small 

 mesoplastron present. 

 January 16, 1893. 



* This genus was proposed bj' Bonaparte, in 1S36, in his Chelonioram Tabula Analytica, 

 p. 7, and njt in 1838, Arch. f. Nat, i, p. liO, as stated by Boulenger. 



fBaur, G., " Osteologisc lie Notizeu iiber Reptilien," Fortsetzung, ii, Zool. Anz., No. 214, 

 1887, p. 101. 



I In the Zool. Anz , No. 285, 1388, 1 liad given the names Amesoplastralia and Mesoplas- 

 Iralia to the two groups, among which I placed at this time several fossil forms which 

 do not belong there. 



jBaur, G., " The Gensra of the Podocnemididoe," Am. Nat., May, 1890, p. 483 (Zool. Anz., 

 No. 285, 1883; No. 296, 1888;. 



IIBaur, G., "Notes on Some Little Known American Fossil Tortoises," Phila. Ac. Kat. 

 Sci., 1891, p. 424. 



