THE OPHIDIA. 



205 



Fmx 



But, in the remarkable group of the Ty2)hlopid(B, the slen- 

 der palatine bones meet upon the base of the skull in the mid- 

 dle line, and are directed transversely, in such a manner as 

 to bound the posterior nasal apertures behind, as in the Satra- 

 chia. There is no transverse bone. The pterygoids lie par- 

 allel with one another under the base of the skull, and are not 

 eonueoted with the quadrate bones. The maxillse are short 

 plates of bone which are connected with the outer extremities 

 of the palatine bones, and are directed obliquely toward the 

 middle line of the oral cavity, into which their rfree edges, 

 armed with teeth, depend. 



Again, the first-mentioned, or typical, form of Ophidian 

 skull exhibits two extreme modifications, between which lie 

 all intermediate gradations. At the one end of the scale are 

 the non-venomous Snakes, and especially Python and Tortrix 

 (which belong to the division Aglyphodontia) ; at the other 

 the poisonous Snakes, and especially (Jrotalus [Solenoglyphia). 



Thus, Python (Figs. 73 and 73) has well-marked premaxillsB, 

 large maxillary bones, palatine bones 

 which are firmly united with the ptery- 

 goids, and transverse bones which bind 

 the noiaxillaries and palato-pterygoid 

 bars into one solid framework. 



The maxillaries give attachment to 

 a long series of recurved teeth, which ^° 

 are not very unequal in size. And Py- 

 thon (like Tortrix, but unlike all other 

 Ophidia) possesses teeth in the premax- 

 ill». 



The squamosal bones are very long, 

 and adhere to the skull, upon which 

 they are slightly movable, only by their 

 anterior ends ; and the quadrate bones 

 are borne upon the posterior ends of 

 the squamosals, and are thus, as it were, 

 thrust away from the walls of the skull, ggl 

 The rami of the mandible are loosely 

 connected by an elastic symphysial liga- 

 ment. Thus, not only can these rami 

 be widely separated from one another, 

 but the squamosal and quadrate bones 

 constitute a kind of jointed levfer, the 

 straightening of which permits of the 

 separation of the mandibles from the 



Fig. 78. — Under-7iew of ti * 

 left half of the sknll and 4- 

 clal bones oi Python. 



