INTRODUCTION. XXIII 
teroglypha are subdivided still farther into the Conocerca, the conical tailed 
or colubriform, and the Platycerca, flat-tailed or sea snakes. The Solen- 
oglypha are also subdivided into Abothrophera, pitless vipers, and Bothro- 
phera, which are marked by a pit on the side of the face between the eye 
and nostril. 
The cosmopolitan genus Elaps contains all the North American species 
of Conocerce. There are two species in the Southern States, and a half 
dozen or more in Mexico. Our species are not considered dangerous. 
Among the old world species of the division are some of the most deadly 
of the order, such as the Cobras, Naja, of Southern Asia and Northern 
Africa, the favorites of the Indian jugglers. As in other sections, there 
are species which feed upon other snakes. 
The Sea Snakes, Platycerca, have the nostrils on the top of the snout, 
and the tail compressed so as to forma paddle. Three to five feet in length 
is the common size; ten feet is a great length for the largest. They are 
numerous in parts of the Indian Ocean. As far as known, a single species 
has been found in fresh water, Hydrophis semper, from Lake Taal in the 
Philippines. Pelamys bicolor has been taken off the coasts of Southern 
Mexico. Sea snakes are said to approach the shores only when about to 
give birth to the young. They feed upon marine animals of various kinds, 
and are sometimes taken in the nets of the fishermen, who fear them very 
little. 
The Abothrophera belong to the Eastern Hemisphere. Serpents of this 
division differ from those of the next principally in the absence of the pit 
or lachrymal fossa. With this exception, structure, habits, effects of venom, 
ete., are similar. 
The pit vipers, Bothrophera, are the most venomous of the new world 
Ophidia. A single family, Crotalide, has heretofore included all of them. 
As in the pitless vipers, the fangs are the only teeth upon the maxillaries. 
The latter are short, and rotate upon the lachrymal and frontal bones in 
such a manner as to allow the fangs to recline against the roof of the 
mouth, where they are covered by an elastic membrane when not in use. 
The fangs are replaced when shed or broken by others, which grow in a 
reclining position behind those in function. A section of one of these fangs 
indicates that the tooth has been folded from its sides forward and closed 
around the groove which opens a short distance above the point. Another 
opening at the base is opposed to the extremity of the duct from the venom 
