1912] Ditmars: Feeding Habits of Serpents 217 



dorsal spines, and a crawfish, or fresh-water crustacean of fully four 

 inches in length, with formidable mandibles. Some of the persist- 

 ently aquatic North American species of Tropidonotus, as T. cyclo- 

 pium and T. taxispilotus indicate a certain degree of specialization 

 in having the eyes placed further forward and nearer the top of the 

 head denoting better adaptation to life in the water. These species 

 are particularly partial to fish, and a great number of captive exam- 

 ples refuse all other food. 



Seminatrix, Helicops, Tropidoclonium, Clonophis, Storeria and 

 Haldea are apparently off -shoot genera of Tropidonotus. The mode 

 of life has varied and while some are persistently aquatic, others are 

 quite terrestrial. We note among the members of all the genera, 

 the tendency of the development of enlarged posterior teeth to assist 

 these non-constricting types in retaining their hold upon their cold- 

 blooded prey with its comparatively naked integument that is easily 

 pierced by such dentition. The single, North American, species of 

 Seminatrix, is apparently a degenerate type of water snake. The 

 strongly keeled scales of Tropidonotus are indicated by hair-like lines 

 on a smooth scalation. This snake leads a secretive life near the 

 borders of streams and feeds upon small batrachians. As a captive 

 it refuses fish. Tropidoclonium and Clonophis are of similar habits. 

 Storeria and Haldea appear to be of degenerate relationship to the 

 Tropidonotus and Eutaenia types. The size is small, seldom exceed- 

 ing twelve inches, and the food consists almost entirely of earth- 

 worms. With the South and Central American Helicops we see pro- 

 nounced specialization toward the aquatic type. The eyes are set 

 at an oblique plane with the top of the head, and these serpents 

 prefer fish to any other food. 



Passing from the genera just considered, we come into consid- 

 eration of several genera which fall into a rather crude group. At- 

 tending their appearance in technical check lists is a number of 

 other genera which are herewith eliminated owing to their species 

 not having been studied. Those that we will group here are Zaocys, 

 Zamenis, Salvadora, Phyllorhynchus, Drymobius, Spilotes, Coluber, 

 Herpetodryas and Dendrophis. Among these we find the predominat- 

 ing number of species to be those feeding largely upon warm-blooded 

 prey, some that evince the power of constriction feeding exclusively 

 upon such prey, others to a lesser extent, a few merely indicating 

 this characteristic in their manipulation of the prey or food, and 

 others evincing no trace of the habit. With Zaocys of Southeastern 



