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 Abothropliera, pitless vipers, and Bothro- 

 pliera, which are marked by a pit on the side of the face between the eye 

 and nostril. 



The cosmopolitan genus Maps contains all the North American species 

 of Conocerca?. 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, Plafycerca, have the nostrils on the top of the snout, 

 and the tail compressed so as to form a 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, IlyiJrophis semperi, from Lake Taal in the 

 Philippines. Pelamys tricolor 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 Abothropliera 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, 

 etc., are similar. 



The pit vipers, Bothrophera, are the most venomous of the new world 

 Ophidia. A single family, Crotalidce, 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 



