1. CHELYDRA. 21 
Emysaura serpentina, Dum. § Bibr. ii. p. 350, pl. xvii. fig. 1 (1835) ; 
A, Dum. Cat. Méth. Rept. p. 15 (1851) ; Bocowrt, Miss. Sc. Mex., 
Rept. pl. v. tig. 1 (1870). | 
Chelydra emarginata, Agassiz, d. c. p. 417 (1857), 
Carapace rugose and with three tubercular keels in the adult and 
Skull of Chelydra serpentina. 
