32 



FOSSIL TURTLES OF NORTH AMERICA. 



groups of turtles combined. Accepting the genera and species as described by Mr. 

 George A. Boulenger in his Catalogue of the Chelonians, there are 30 genera of 

 Cryptodira with 140 species; 21 genera of Pleurodira, with 24 species; 6 genera of 

 Trionychidae,with 24 species. The headquarters of the superfamily is North America. 



Fig. II. Map showing geographical distribution of the Chelydrida;. Portions of the western 

 hemisphere and the island of New Guinea. 



Fig. 1 1 shows the distribution of the Chelydridae. The northern limits of the 

 family are somewhat uncertain. The same species, Chelydra serpentina, that occurs 

 in Canada, is found also in Ecuador, South America. Until recently it has been 

 supposed that the members of this family are confined to the New World; but }. 

 Douglas Ogilby has reported (Proc. Roy. Soc, Queensland, xix, 1905, p. 11) the 

 discovery of a new genus and species, Devi si a mythodes, in the Fly river, New 

 Guinea, the river that has furnisht likewise the remarkable turtle Carettochelys. 

 The New Guinea snapper has a length of 860 mm., the carapace being 330 mm. 

 long. This distribution of the snappers is even more remarkable than that of the 

 camels and tapirs. 



Fig. 12. Map showing distribution of the Dermatemydida;. 



Fig. 12 displays the distribution of the Dermatemydida;. This is one of the 

 decadent families of the order, for it abounded in genera and species in the Upper 

 Cretaceous of North America and still existed in reduced numbers during the Ter- 

 tiary. The family, now consisting of three genera and four species, is confined to 

 portions of Mexico and Central America. 



As seen from fig. 13, the Emydida? have a wide distribution, occupying all the 

 habitable portions of North America, South America, Europe, Asia, and most of the 



