238 THE ANATOMY OF VERTEBRATED ANIMALS. 



trnly correspond with the turbinals of tlie liiglier Verte- 

 hrata. Tlie squamosals are visually well developed. Tliere 

 is no jugal, or quadrato-jugal. 



Though the general confoiination of the skull in the 

 Ophidia is that which has now been described, it presents 

 remarkable modifications in different members of the 

 order, especially iu the form and disposition of the bones 

 of the jaws. In the great majority of the Ophidia, the 

 elongated palatine bones have their long axes longitudinal, 

 lie on the outer sides of the internal nasal apertures, and 

 do not enter into the formation of the posterior boundaries 

 of those apertiires. Each is connected by a transverse bone 

 with the maxilla, which lies at the side of the oral cavity ; 

 and the pterygoids diverge posteriorly towards the quadrate 

 bones, with which they are connected by ligaments. 



But, in the remarkable group of the Tijphlopidoe, the 

 slender palatine bones meet upon the l^ase of the skull in 

 the middle line, and are directed transversely, in such a 

 manner as to bound the posterior nasal apertures behind, 

 as in the Batrachia. There is no transverse bone. The 

 pterygoids lie parallel with one another tinder the base of 

 the skull, and are not connected 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 towards 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 Aglyphodontia) ; at the 

 other the poisonous Snakes, and esi^ecially Crotaliis {Soleno- 

 glyphia). 



Thiis, Python (Figs. 72 & 73) has well-marked premaxiUae. 

 large maxillary bones, palatine bones which are firmly united 

 with the pterygoids, and transverse bones which bind the 

 maxillaries and palato-pterygoid bars into one solid frame- 

 work. 



