of the '■Zoology of Mexico^ 113 



2. Slaurotypus Salvinu, Gray, Dum^ril & Bocourt, /. c. p. 22, 

 t. V. f. 3, 3 a ; Gray, P. Z. S. 1864, p. 127 ; 1869, p. 179, 

 fig. 5 (skull) ; Suppl. Cat. Sli. Rept. p. 65. 



Received from Vera Paz, Guatemala, one of the affluents of 

 the Polochie. 



The figure only represents the underside of the living 

 animal. 



1 do not see how Staurotypus marmoratus of J. von Fischer, 

 from Tejas in Mexico, described and figured in Wiegmaun's 

 Archiv fiir Naturg. 1870, p. 265, t. x., differs from this 

 species. 



1. Cinosternon cruentatum, A. Dumeril, Arch, du Museum, 

 1852, vi. p. 238, t. xvi. 



2. Cinosternon albogulare, Dumeril & Bocourt, /. c. p. 24. 

 The Museum received three specimens from San Jos^, Costa 

 Rica. 



3. Cinosternon leucostomum^ A. Dumeril, Arch, du Museum, 

 1852, vi. p. 239, fig. 17. 



4. Cinosternon hirtipes^ Wagler, Icon. Amphib. t. xxx. 

 The three former are only in the Paris Museum ; and the 

 characters separating them seem very doubtful. The last is 

 only known from Wagler's figure. The large number of 

 specimens in the British Museum from different parts of 

 tropical America show that the species of this genus are very 

 liable to vary. 



Chelonia Agassizii, Dumeril & Bocourt, I. c. p. 26, t. vi. 



Described from a single specimen in the Museum of Paris, 

 taken at the mouth of the Naguale, on the Pacific shores of 

 Guatemala. 



From the form of its head-shields, it appears to be a species 

 of the restricted genus Chelonia. The authors say it is well 

 distinguished from Chelonia virgata by the dorsal disk being 

 more elevated and sloping on each side like a roof, and more 

 elongate and narrowed over the hinder limb, and by the 

 presence of an interoccipital plate on the back of the crown. 

 It may probably be a distinct species, perhaps one of those de- 

 scribed by Mr. Girard. 



It is very difficult to distinguish species of turtles when 

 they are divided into small groups by the form of the skull, 

 number of head-shields, &c., unless you have a series of speci- 

 mens showing all the ages of the species ; for the bones undergo 

 such a change of form during the development of the animal, 



Ann. & Mag. N. Hist. Ser. 4. Vol. xii. 8 



