CROCODILIANS, LIZARDS, AND SNAKES. 179 



Of these three suborders, the Pythonomorpha is extinct, having 

 begun and ended with Cretaceous time. The Sauria and Ophidia are 

 the subjects of the present work. Both begin in Cretaceous time, so 

 far as our present knowledge extends, but it is at the existing geo- 

 logic period of time that they present the greatest multiplication of 

 individuals and species. This statement is, of course, provisional and 

 dependent on future discoveries in paleontology for its verification or 

 contradiction. 



The superficial characters given by systematic writers generally as 

 distinguishing the Sauria and Ophidia are quite insufficient for that 

 purpose. Johannes Miiller ^ first placed the distinction on a sound 

 basis by showing that in the Ophidia the frontal and parietal bones 

 descend to the basi-cranial axis as in no other vertebrates, thus closing 

 the brain case in front, while in the Sauria this does not occur, and 

 as the ali- and orbito- sphenoid bones are rudimental or wanting, the 

 brain case is without osseous wall in front. Some lizards present a 

 distinct approximation to the ophidian type in the strong decurvature 

 of the ijarietal bones at the rides; these are the Annulati and the 

 Annielloida. These groups display a similar approximation in the con- 

 tinuous sutural union of the occipital and parietal elements, a condition 

 universal in Ophidia and rare in Sauria. 



I have pointed out^ another point of distinction between the two 

 divisions, viz, that the supratemporal ("squamosal"' olim) is present in 

 the Sauria and absent in the Ophidia. As it is, however, absent in 

 the Annielloida and Amphisba-nia, I have not included it in the defi- 

 nition of the former suborder. This definition has not been adopted by 

 those authors who erroneousl}^ regard the suspensorium of the (juad- 

 rate bone in the Ophidia as identical with the sui)ratemporal of the 

 lizards. I pointed out in the above essay (1871) that this element in the 

 snakes is homologous with the paroccipital of the Sauria, an opinion 

 which was not agreed with at that time, but which has now received tlie 

 assent of various anatomists, notably Professor Baur. 



Baur and some others do not, however, agree that the element in ques- 

 tion is the paroccipital, but call it squamosal and other names. I was 

 led to identify it with the former element of the Testudinata, etc., by a 

 consideration of its structure in the Pythonomorpha,^ where it is much 

 more largely developed than in the Sauria, and where it supports the 

 quadrate bone as in the Ophidia, which it does not do, or does only 

 partially in a few cases, in the Sauria. I have made this more clear 

 than heretofore I hope in a recent essay.^ The paroccipital bone is 

 received deeply between the exoccipital and the petrosal in the Pytho- 

 nomorpha in the same manner as in the Tortricine snakes, a structure 

 which does not occur in the Sauria. This structure is somewhat 



'In Tiedemanu u. Treviranus, Zeitschrift f. Physiologie, IV, p. 233. 



2Proc. Am. Ass. Ad. Sci., XIX, 1871, p. 221; Trans. Am. Phil. Soc, XIV, 1870, p. 29. 



3Idem; The Cretaceous Vertebrata of the West, Kept. U. S. Geol. Sur. Ter., II, 



1875, p. 113. 

 * American Naturalist, September, XXIX, 1895, p. 855. 



