INTRODUCTION. 2. ©. 
put themselves in the attitude of detense, and resent attack when unable 
to escape; their bites are mere seratches, and should occasion no anxiety. 
Although typical earth, water, or tree snakes are very distinct, the 
intermediates are so numerous as to make it impossible to classify them 
according to habits. It is well, however, to note the differences of the 
types, without losing sight of the fact that there are forms of such struc- 
ture and habits as to make their position doubtful in either of the three 
divisions. 
Ground Snakes are rather stout and thick in body and tail. Their bodies 
are usually cylindrical, and the tails most often short and conical. For the 
most part they have smooth scales. The eye is of moderate size to small, 
and the pupil generally round. Certain species which burrow, as those of 
Heterodon, have valvular nostrils, and rostrals shaped somewhat like shovels 
or plows. 
Water Snakes are well represented in the genus Nerodia, in which 
the body is stout and fusiform, the tail tapering, the nostrils valvular and 
near the top of the snout, and the scales keeled. One of the most peculiar 
forms of the division is Herpeton, which has a pair of feelers or tentacles 
extending forward from the muzzle. 
Tree Snakes are very long and slender. Their eyes are comparatively 
large, and the pupil is either round or oblong, erect or horizontal. Tactile 
appendages to the snout are possessed by some species. In general they 
feed upon the small animals that make their homes among the leaves and 
branches. Rachiodon, an African genus, feeds on eggs; it has very weak 
teeth in the jaws, but the inferior processes of the vertebree of the neck 
extend into the esophagus, and are tipped with enamel for the purpose 
of crushing the shells after so far swallowed that the contents may not 
escape by the mouth and be wasted. Green is a very common color in 
this division. 
In the list of families in this suborder north of Tehuantepec, several 
really belong to South America, being introduced on account of stragglivg 
species reported from the Mexican region. Of the Dipsadinw, a single 
species ranges north of Mexico into Arizona and Texas. From Southern 
Mexico two species of Scytaline have been noted. There are two species 
of Dendrophinw, which also range into Mexico. The most abundant North 
American snakes belong to the Nafricinw, of which species, as Eutenia 
sirtalis, range over the whole continent, excepting the far North. The 
