SYNOPSES AND DESCRIPTIONS. 109 
PLATYCERCA, 
HYDROPHIDAE. 
Sea serpents. Venomous. Elongate, subeylindrical anteriorly, com- 
pressed posteriorly; head rather indistinct, generally depressed ; tail short, 
compressed into a paddle. Eye small, pupil round. Fang small, erect, 
grooved in front, followed by other teeth. Nostril valvular, Head-shields 
generally irregular. No loreal. Scales small, with or without keels, or 
tubereular. No claw at the side of the vent. Hab. tropical portions of 
the Indian and Pacific oceans, sometimes entering fresh waters. 
PELAMYS. 
Daudin, 1803. 
Moderately long; neck rather large; head depressed; snout long, broad. 
No internasals. Nasals in contact, nostrils near the hinder margins. No 
loreal. Scales small, not imbricate. Ventrals indistinct or small. Lower 
jaw not notched in front. One species of this genus is frequently met with 
off the western coasts of Southern Mexico. 
PELAMYS PLATURA. 
Much compressed posteriorly; neck stout; head little larger than the 
neck, long, depressed; snout long, broad, and rounded in front; tail short, 
of moderate width. Head-shields abnormal. No internasals. Nasals 
longer than broad, nostril near the outer posterior angle. Prefrontals 
hexagonal, receiving the anterior angle of the frontal between them. No 
loreal. One anteorbital, sometimes two. Two to three postorbitals. 
Labials 7 
not imbricate; lower with a convexity or tubercular keel; upper flat. 
9, second larger. Seales polygonal, commonly hexangular, 
In the specimen before me there are 53 rows around the middle of the 
body. Ventral scales similar. 
Back (23 rows of scales) and top of head black. Upper Hip and lower 
half of body yellow. Lower lip marked with black. Tail with three 
transverse bands of black, the rounded ends of which extend near the 
lower margin, where they alternate with four spots of black. Vent in a 
spot of black. Tip of tail black. The coloration varies greatly in differ- 
ent individuals. The specimen described was taken on the western coast 
of Nicaragua. 
