718 



REPORT OF NATIONAL MUSEUM, 1902. 



The green turtle is easily distinguished from the other Porto Rican 

 marine turtles by the single pair of elongated prefrontal shields on 

 top of the snout. The shell alone can be recognized by having only 

 four costal shields and by the shields not overlapping posteriorly. 

 The loggerhead {Caretta caretta) has five costal shields, while the 

 hawksbill {Eretm.ochelys imbricata) has overlapping shields (tig. 193). 



None of our expeditions to Porto Rico brought back any specimens 

 of the green turtle, but its occurrence in the waters surrounding the 



Fig. 193.— Eeetmochelys imbricata. \ natural size. Shell from above. No. 25645, U.S.N. M. 



island is well known. Dr. B. W. Evermann, in his general report on 

 the investigations in Porto Rico of the United States Fish Commis- 

 sion steamer Fish Hawk in 1899, writes that it is rare except at the 

 east end of the island, and he accounts for the scarcity of turtles by 

 the absence of large areas of shallow water with sandy bottom. 



Genus ERETMOCHELYS" Fitzinger. 



1828. Caretta Ritgen, Nova Acta Acad. Caes. Leop., XIV, p. 270 (type, Chelonia 



imbricata; not of Rafinesque, 1814). 

 1843. Eretmochelys Fitzinger, Syst. Rept., p. 30 (same type). 

 1873. Onychochelys Gray, Proc. Zool. Soc. London, 1873, p. 397 (type, O. kraussi). 



a'epEr/Liov, oar; #£'At>s, turtle. 



