196 THE CLASSIFICATION OP THE OPHIDIA. 



excepting when they occur as borders of the sulcus spermaticus, where they are con- 

 stant. These must not be confounded with temporary longitudinal folds of the struc- 

 ture, which can be removed by stretching. 



I now give the exact definitions of the divisions as far as definable with present 

 information. The definitions of the suborders are those of Miiller, modified by myself* 

 An examination of the osteology of the skull led me, in 1859,f to place the genera 

 Causus and Atractaspis in the order Solenoglypha. The former had been placed in 

 the Proteroglypha by Dumeril and Bibron, and the latter was made the type of a 

 family " with permanently erect fangs " as division C of the second section of the 

 Ophidia, the " Colubrinse," by Gunther.J My arrangement has been adopted by 

 all later authors. 



Authors have differed as to the homology of the bone which supports the quad- 

 rate in the Ophidia. Huxley§ has identified it as the element he called squamosal in 

 the Lacertilia, a conclusion to which I have demurred || for two reasons. The first of 

 these is that this element is one of the bones of the brain-case in the Angiostomatous 

 snakes, where it is intercalated between the exoccipital, parietal and petrosal. The 

 second is, that the bone called by Huxley squamosal in the Lacertilia has no such in- 

 tercalary relation, but is one of the segments of the primitive roof of the temporal 

 fossa. In the degenerate snakelike forms of the Lacertilia this element disappears, and 

 I believe that it does not exist in the Ophidia. I add that I agree with those osteolo- 

 gists who do not regard it as the homologue of the squamosal of the Mammalia, and 

 who give it the name, after Owen, of supratemporal.^l 



If we now remove the supratemporal from the skull of a Lacertilian we have the 

 condition which exists in the Ophidia. We observe beneath the position of its posterior 

 end, and between the exoccipital, parietal and petrosal, an element which corresponds 

 with the bone in question in the Ophidia. This element has received various names, 

 among the rest that of squamosal. I think I have shown, however, in view of the 

 characters which it presents in the Pythonomorpha, that it is the paroccipital. By the 

 lengthening of the exoccipital in the Lacertilia the paroccipital has been carried far 

 from the brain-case and supports the quadrate behind. By its elongation posteriorly 

 it has carried the quadrate posterior to the other bones of the skull in the Eurystomat- 



* Proceeds. Academy Philada., 1864, p. 230; Proceeds. Amer. Philos. Soc, 1886, p 479. 

 f Proceeds. Academy Philada., 1859, p. 335. 

 X Oatal. Golubrine Snakes Brit. Museum, 1858, pp. 1 et 239. 

 § Anatomy of Vertebrated Animals, 1872, pp. 189 and 203. 



[ "On the Homologies of the Cranial Bones of the Reptilia," Proceeds. Amer. Assoc. Adv. Science, 1871, pp. 174 

 and 217. 



1f Transactions Amer. Philos. Soc, 1892, p. 20. 



