I THE OPHIDIA. 233 



t 



articulating with the iive proximal bones of the digits. In 

 both manus and pes the number of the phalanges, count- 

 ing from the preaxial to the postaxial side, is 2, 3, 4, 4, 3. 



IV. The Ophidia.— This order of Reptiles has been 

 divided as follows : — 



A. The palatine bones widely separated, and their long axes 



longitudinal ; a transverse bone ; the pterj'goids united 

 with the quadrate bones. 



a. None of the maxillary teeth grooved or canaliculated. 



1. Aglypliodontia. 



b. Some of the posterior maxillary teeth grooved. 



2. Opisthogli/phia. 



c. Grooved anterior maxillary teeth succeeded by solid teeth. 



3. Proteroglyphia. 



d. Maxillary teeth few, canaliculated, and fanglike. 



4. Solenoglypliia. 



B. The palatine bones meet, or nearly meet, in the base of the 



skull, and their long axes are transverse ; no transverse 

 bone ; the pterygoids are not connected with the quadrate 

 bone. 



5. Typhlopidce. 



All the Snakes possess a scaly epidermic investment, 

 which is usually shed in one piece, and reproduced at defi- 

 nite intervals. As a general rule these scales are flat, and 

 overlap one another; but sometimes, as in Acrochordus, 

 they become more tubercle-like, and do not overlap. In the 

 Rattlesnakes (Cwtalus) the body is terminated by several 

 loosely-conjoined rings of horny matter, which consist of 

 the modified epidermis of the end of the tail. 



The derm does not become ossified in the Oplddia. 



The number of the vertebrae in the snakes is always con- 

 siderable, and in some cases becomes very great, amounting 

 to more than four hundred in some of the large Pythons. 

 The spinal column is divisible only into cavidal and pre- 

 caudal regions, as there is no sacrum, nor any distinction 

 between ceiwical, dorsal, and lumbar vertebrae. The atlas 



