204 Zoological N. Y. Zoological Society. [I; H 



ment and relationship. It is understood that snakes subsist upon 

 prey of great proportionate size, power and in possession of liberal 

 means of defence. Yet these limbless reptiles, aside from the con- 

 stricting habits of some and the poison-injecting teeth of others, 

 depend absolutely upon the manipulation of the jawbones in the 

 handling, possibly subjugation of the proportionately heavy quarry. 

 Constriction was apparently the oldest type of subjugation, but 

 changes in the dentition among various groups, influenced by the 

 extension of distribution and change of food, brought about new 

 methods of killing the object of food. Among the non-venomous 

 members of the Coluhridae that indicate no inclination to constrict, 

 the structure of the teeth is in direct relationship to the habits. Thus 

 the frog and fish-eating species have enlarged posterior teeth to 

 quickly pierce and firmly grip the struggling victim. Snakes of 

 this type evince an unique habit against the defensive actions of frogs 

 and toads in greatly puffing up their bodies to prevent being swal- 

 lowed. With repeated grippings of the enlarged posterior teeth, the 

 serpent pierces the victim's air cavities thus frustrating and overpower- 

 ing it. With these snakes the dilatability of the swallowing structure 

 and the agility of deglutition are markedly developed. The cosmo- 

 politan genus Tropidonotus (Water Snakes) and the American genus 

 Eutsenia (Striped Snakes) exhibit uniformly typical species of the 

 habits described. With the North American "Adders," (Heterodon), 

 we observe greater development of the dentition in utilization of 

 these traits. In the upper jaw is a pair of posterior fang-like teeth 

 that exhibit faint traces of an anterior groove when microscopically 

 examined. Such development may point to the future elaboration 

 of these greatly enlarged teeth into grooved, venom-conducting 

 fangs, of similar structure to those of the Opisthoglypha. Similar 

 grooved teeth are to be noted among other Colubrine snakes, appar- 

 ent with some to a very faint degree. 



Among the non-constricting Colubrine serpents the egg-eating 

 Dasypeltis scabra, of Africa, stands as another type of radiating spe- 

 cialization in the manipulation of the food. Here, a weak-bodied 

 creature is able to swallow an egg three times the diameter of the 

 thickest part of the reptile's body. The jaws have become almost 

 destitute of teeth, but the presence of a few posteriorly situated ones, 

 provide the power for the jaw bones to alternately grip and engulf 

 the food, assisted by peristaltic movements of the muscles of the 



