40 REPTILES. 



****** Head small ; frontal shields 2, transverse^ hand-like ; rostral 



triangular^ suhangular. 



37. Prosymna. 



D. Head covered ivith small scales : tail iviih one row of shields be- 

 neath ; abdominal shield broad, rounded, smooth: nostril in a 

 shield, anterior, sublateral : scales granular, with roivs of keeled 

 scales. Xenodermina. 



38. Xexodermus. 



I. Tail compressed, except in Acrocliordus. Belli/ keeled, icith two 

 rows of small scale-like shields, often united together into a single, 

 broad, six-sided, often two-keeled shield. The anterior teeth large, 

 and grooved on the front edge. Venomous. 



Hydrina, Gra?/, Zool. Misc. 59, 1842. Hydridae, Graj/, Ann. 

 Phil. X. 1825, 206. Colubroidea, § 1, and Bungaroidea, § 1, Fitz. 

 N. Sj/st. Rept. 32, 1826. Hemiophidia, fam. Nectopns, and Cha- 

 linophidia, fam. Hydrophis, Fitz. Consp. Ophid. 1846. Hydrus, 

 Schneid. H. Amph. i. 233. Latr. Rept. iv. 293, Baud. Rept. \n. 

 372. Cuv. R. A. ii. 74, ed. 2, ii. 97. Merrein, Tent. 138. Hydro- 

 phis, Oppell, Rept. 59, 1811. Pelamis, Baud. Rept. \\\. 357. 



These are true sea-snakes : they coil themselves up on the shore, 

 living on sea-weeds, and lay their eggs on the shore : they are often 

 found asleep on the surface of the sea, when they are easily caught, 

 as they cannot descend without first throwing themselves on their 

 back, probably to repel the air in their large vesicular lungs, (see 

 Greys West. Australia, 445). Often thrown ashore by the surf: 

 they are sometimes found in rivers, having been brought in by the 

 tide, but they can live only a short time out of salt w ater. They 

 are often caught in nets, and are held in great dread by the fisher- 

 men, on account of their venomous bite. 



The pupil is round: Lesson {Voy. Belanger) erroneously repre- 

 sents it as linear and erect. 



The separation of the specimens of this family into species and 

 genera is attended with great difficulty ; the form and number of 

 t-ie shields of the head, lips, temple and chin, are liable to great 

 variation, not only in the different specimens, but often in the two 

 sides of the same individual. The two ventral series of scales are, 

 in the same specimen, sometimes separate, and at other times united 



