THE OPHIDIA. 



205 



^iitsc 



But, in the remarkable group of the Typlilopidm^ 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 JBatra- 

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

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

 connected with the quadrate bones. The maxillse are short 

 j^lates 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 free 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 Aglypliodoyitia) ; at the other 

 the poisonous Snakes, and especially Crotalus {^Solenoglypliia), 



Thus, Python (Figs. 72 and 73) has well-marked premaxillae, 

 large maxillary bones, palatine bones 

 which are firmly united with the ptery- 

 goids, and transverse bones which bind 

 the maxillaries 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 

 Ophidla) possesses teeth in the premax- 

 illae. 



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, g^ 

 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 lever, the 



•strnifrhtpninrr of whioli ■n<=»rmU« of flip» ^^- T3.— Under- Wew of tb€ 



Btraignreumg oi wnicn permitt, ot tne left half of the skull and fa 

 separation of the mandibles from the <aaX\)Qiies, oi Python, 



