46. HYDRUS 



tals. Nostrils open upward in large nasal plates. No inter- 

 nasals. Loreal present or absent. Ocular plates variable. 

 Seven to 1 1 supralabials. Anterior genials sometimes present. 

 Scales on body smooth, hexagonal, juxtaposed, in from 45 

 to 61 rows. No large gastrosteges or urosteges. Tail short, 

 high and thin, paddle-shaped. In males the scales have 

 central tubercles. 



The color above is dark brown or bluish black on about 

 1 5 or 1 7 rows of scales, changing abruptly, along a more or 

 less straight line, to the light yellow, brownish yellow, or 

 yellowish brown of the sides and lower surfaces. The tail 

 is light yellow with dark blotches. 



Length to anus 528 



Length of tail gj 



Distribution. — This snake occurs nearly everywhere 

 along the coasts and islands of the Indian and warmer por- 

 tions of the Pacific oceans. It has been found in the Hawaiian 

 and Galapagos islands and is common along the coast of 

 Central America. 



Mocquard records two specimens captured in the Gulf 

 of California near Espiritu Santo Island. 



Cope mentions it from "Pacific coast Guaymas?" 



Habits. — This is a marine species, and probably eats 

 fish. 



Family 1 6. CROTALID^ 



The Crotalidce or Pit Vipers are represented in western 

 North America by fifteen kinds of rattlesnakes. These are 

 our only poisonous serpents, except the little coral snake 

 (Elaps or Micrurus), and may be distinguished from the 

 harmless forms by their possession of a pit in the side of the 

 face between the eye and the nostril, and a horny, segment- 



