XXII INTRODUCTION. 
genera Eutenia, Nerodia, Regina, and Storeria, are North American; Hel- 
cops and Hydrops are better represented in Central and South America. 
Although the family names in common use are retained here, they are 
ranked as subfamilies of one great family, including all the Acacophidia 
or Colubrine snakes, the Colubride. The family Colubrine contains in the 
genus Coluber several species very common in the United States: the Black 
snake, C. constrictor, is found over a great portion of the continent, and the 
section of the genus containing the Coach Whip snake (Masticophis), C. 
Jlagelliformis, includes half a dozen species, from the Southern States, Mex- 
ico, and as far south as Chili. Two species of the South American genus 
Spilotes are found in the Gulf States. Pétyophis, Cyclophis, Phyllophilophis, 
and Salvadora are North American. As the name Salvadora does not seem 
to be used elsewhere in the animal kingdom, it has been retained. Dromi- 
cus is South American and West Indian, but contains one species peculiar 
to the Southeastern United States and several others found in Southern 
Mexico. The old world genus Elaphis claims several widely distributed 
species from the southern half of the continent. 
Tachymenis, Erythrolamprus, Liophis, and Xenodon are South American 
Coronelline, and are represented by a few species in the southern part of 
Mexico. Ophibolus, Diadophis, Heterodon, Rhinocheilus, Cemophora, and Hyp- 
siglena are’ classed as North American; the first three are found in all 
the States, with, perhaps, a few exceptions in the northern tier. 
The Calamarinew, of the genera Tantilla, Contia, Sonora, Virginia, and 
Carphophis are Northern; Micimia, Cheilorhina, Stenorhina, Ninia, Geophis, 
and Elapomorphus are shared by Mexico with South America. 
Tree snakes are found in the Dipsadinew, Scytaline, Dendrophine, and 
Colubrine ; water snakes in the Natricine; and ground snakes in the 
Calamarine, Coronelline, and Colubrine. But in each family there are 
species whose habits are so uncertain as to render their positions doubt- 
ful. 
ToOXICOPHIDIA. 
Grouping all the venomous serpents in a single suborder, brings together 
animals of considerable diversity. Because of their differences they have 
been arranged in various sections: one, the Proteroglypha, in which the 
fangs are erect, immovable, and grooved in front; and another, the Solen- 
oglypha, which are distinguished by an erectile perforate fang. The Pro- 
