892 18. AYDRIDA 
Genus 46. Hydrus 
Hydrus ScHNEIDER, Hist. Amph., Vol. I, 1799, p. 233 (type, 4ico/or). 
Hydrophis Larrei.xe, Hist. Nat. Rept., Vol. IV, 1802, p. 193. 
Pelamis Daupin, Hist. Nat. Rept., Vol. VII, 1803, p. 357. 
Pelamys Wac.er, Syst. Amph., 1830, p. 166. 
Elaphrodytes Gistet, Naturg. Thierr., 1848, p. IX. 
The body is rather short, somewhat compressed, with 
strongly compressed, short, oar-shaped tail. The head is 
rather narrow and much depressed with long, broadly round- 
ed snout. The nostrils open upward in the large nasal plates 
on top of the snout. The head plates are large. There are 
no internasals. The scales on the body are hexagonal or 
quadrate, juxtaposed. There are no enlarged gastrosteges. 
The eyes are small with round pupils. 
206. Hydrus platurus (Linnzus) 
Brcotor SEA-SNAKE 
Anguts platura Linnaeus, Syst. Nat., 12ed., Vol. 1 1766, p. 391 (no 
type locality). 
Hydrus bicolor Scuneiwer, Hist. Amph., Vol. I, 1799, p. 242 (no type 
locality). 
Pelamis bicolor Daupin, Hist. Nat. Rept., Vol. VII, 1803, p. 366; Core, 
Bull. U. S. Nat. Mus., No. 32, 1887, p. 87. 
Hydrus platurus Bou.encer, Cat. Snakes Brit. Mus., Vol. III, 1896, 
p. 267; Sreynecer, Bull. U. S. Nat. Mus., No. 58, 1907, p. 4393 
Mc Lain, Contributions to Neotropical Herpetology, 1899, p. 53 
Mocquarp, Nouv. Arch. Mus. Hist. Nat., Paris, Ser. 4, Vol. I, 
1899, p. 330; Mocquarp, Miss. Sci. au Mex., Pt. III, Rept., 1908, 
P- 930. 
_ Description —Head depressed, flat-topped with long 
broad snout. Temporal regions not swollen. Rostral plate 
large, somewhat broader than high, bounded behind by 
nasal and first labial plates. Plates on top of head are a 
pair of very large nasals, a pair of prefrontals, a large fron- 
tal, supraocular of each side, and a pair of large, long parie- 
