268 ZOOLOGY. 
Sub-order 2. Colubrina. 
In the Colubrina we miss the highly developed poison fangs which are 
so conspicuous in the Viperina; and the upper maxillary bones, or edges of 
the jaw, are well supplied with teeth. Some few of the species, however, 
are poisonous, this being especially the case with the Hydride, or water- 
snakes, of the East Indies. Their venom fangs, however, are small, and 
there are several teeth in a line behind the fangs. The head is of 
moderate size, not conspicuously wider than the neck, and the crown in 
one family is covered by a regular shield. Of the three families of the 
sub-order, Hydride, Boide, and Colubride, the two first have the belly 
covered with small, narrow, elongated scales, like those of the back; while 
in the Colubride the belly is covered with large, broad plates, each one 
extending entirely across the abdominal surface. 
Fam. Hydride. This family, the species of which live almost alto- 
gether in the water of seas, lakes, and rivers, are distinguished from the 
Boide, with which they agree in the small scales on the belly, by the 
entire absence of spurs on each side of the anus, like rudimentary feet. 
The ventral scales are narrow, hexagonal, or bandlike; the eyes. and 
nostrils look upwards, the latter generally placed in the middle of a- 
shield with a slit or groove to its outer edge; the fangs are of moderate 
size, intermixed with the maxillary teeth; the pupil is small and round, 
and the tail is usually compressed into an oar, but sometimes conical. 
Very many are poisonous. The species with compressed tails belong- 
ing to Pelamis, Lapemis, Hydrus, &c., are true snakes, coiling them- 
selves up on the shore, where they lay their eggs. Their food is said 
to consist of seaweeds, although perhaps incorrectly. They are often 
found asleep on the surface of the sea, and are then easily caught, as they 
cannot descend without first throwing themselves on their backs, probably 
to expel the air from their large vesicular lungs. They are often thrown 
ashore by the surf, and are occasionally found in fresh water, having been 
brought in by the tide, but they appear unable to live long out of salt 
water. The fishermen of the Eastern seas often catch them in their nets, — 
and hold them in great dread on account of the venom of their bite. The 
species with conical tails appear to live principally in fresh waters. Some 
recent authors have placed North American species under this family, 
though apparently with much impropriety (Helicops abacurus, and erythro- 
grammus of Holbrook, with some others). Pl. 90, fig. 7, represents Achro- 
chordus javinica, a species of this family from Java. 
Fam. Boide. In this family, which contains species not poisonous, 
indeed, but terrific on account of their gigantic size, we find the ventral 
scales or shields to be narrow, transverse, and often six-sided. The hinder 
limbs are developed under the skin, formed of several bones, and ending in 
a short exserted spur, placed one on each side by the vent. The tail is 
short, generally prehensile, and the pupil is oblong and erect, except in the 
genus Tortriz. 
472 
