154 CALIFORNIA ACADEMY OF SCIENCES. 



Natrix celvEno (Cope). 



Tropidonotus celceno. 



1860, Cope, Proc. Ac. Nat. Sci. Phila., p. 341. 



1861. Cope, Proc. Ac. Nat. Sci. Phila., p. 298. 

 Tropidonotus validus celceno. 



(1875, Cope, Bull. U. S. Nat. Miis., No. 1, pp. 42, 93.) 



(1883, Yarrow, Bull. U. S. Nat. Mus., No. 24, p. 133.) 



(1887, Belding, West Am. Scientist, iii, 24, p. 99.) 

 Regina valida celceno. 



(1887, Cope, Bull. U. S. Nat. Mus., No. 32, p. 74.) 

 Tropidonotus leberis validus. 



[1883, Garman, Mem. Mus. Compr. Zool. Cambr., viii, 3, p. 143, 

 (part).] 

 Natrix valida celceno. 



1892, Cope, Proc. U. S. Nat. Mus., 1891, p. 670. 

 Tropido7iotus validus. 



[1893, Boulenger, Cat. Snakes Brit. Mus., i, p. 237 (part).] 



There seem to be no structural differences between 

 this and the preceding species. In fact, it is not improb- 

 able that JV. celcBno will ultimately be found to have been 

 established upon melanistic individuals of iV^. valida. Un- 

 til this has been shown to be the case, however, they 

 must be regarded as distinct species, for they live in the 

 same localities without any apparent tendency towards 

 intergradation, so far as the specimens before me reveal. 

 The number of preocular plates is either one or two, but 

 the postoculars seem to be constantly three. The largest 

 specimen is 890 mm. in total length, the tail being 208 mm. 

 It has the internasal plate of each side united with the 

 corresponding prefontal, but a groove extends halfway 

 across between them. Some of the specimens contained 

 small fish, Mugil brasiliensis. 



