1912] Ditmars: Feeding Habits of Serpents 205 



neck. The development of the vertebrae in this species into knife- 

 like points extending into the sesophagus to cut the egg shell as it 

 passes, is quite unique among snakes. The regurgitation of the shell 

 afterward, as far as the writer can note, is an absolutely unique 

 trait among serpents. Though many of them feed largely upon eggs, 

 the shells of which are crushed in the throat by the reptile forcing 

 that portion of the body against the ground, the fragments of the 

 egg-shell are swallowed and entirely dissolved by the gastric juices. 



In considering the relationship of dentition to the feeding traits 

 of non-venomous serpents it is of interest to note that among the 

 typical constrictors there is but little generic individuality in the 

 structure of the teeth. With snakes that feed largely upon warm- 

 blooded prey, there is a uniform, liberal provision of strong, recurved 

 teeth. Among those that feed principally upon mammals and birds 

 there is a tendency for the anterior teeth to be the longer and stouter. 

 With snakes that seize a struggling creature to kill it by pressure of 

 the coiling body, this development will be seen to be highly effica- 

 cious, although quite unsuited to the non-constrictor, which must 

 entirely manipulate the struggling prey by the work of the jaws alone. 

 The dentition of the constrictor is designed to firmly seize the quarry 

 without further movement of the jaws and draw it within the coils 

 to be killed by strangulation. Some generic individuality in denti- 

 tion, though along the same lines of enlargement of the anterior 

 teeth, exists among constrictors subsisting largely upon birds. The 

 South American and Madagascan Tree Boas, Corallus, are good 

 examples. The teeth become gradually enlarged anteriorly in both 

 the upper and lower jaws until the extreme anterior pairs might be 

 designated as really fang-like. A structure like this is highly effect- 

 ive in seizing feathered creatures. The long, extremely sharp teeth 

 pierce the abundant covering of the prey and take positive hold. By 

 far the greater number of serpents evincing a tendency to enlarge- 

 ment of the posterior teeth subsist upon cold-blooded animals and 

 are non-constrictors. The writer has recently noted an apparent 

 trait among non-fanged Colubrine snakes that warrants much inves- 

 tigation. This is a certain paralyzing effect of the salivary secretions. 

 The most definite observation related to specimens of South America 

 Tree Snakes — Aehtulla. 



The subject of dentition brings us to a similar review of the feed- 

 ing habits of the venomous snakes. Here we note that among 



