CROCODILIANS, LIZARDS, AND SNAKES. 11)9 



is generally much more elongate than in the Ophidia, each consisting 

 of a slender peduncle and distal hollow bulb. In the genus Gongylius, 

 and probably in other Scincidte, the olfactory process is not longer than 

 in the Ophidia. The ventricles of the mesencephala are distinct from 

 each other, and these bodies are also separate from each other, except 

 at the base. Tlie cerebellum (epeucephalon) does not difter materially 

 from that of the Ophidia excei)t in the case of the Geckonida>. In as 

 many of the genera as have been examined this region is represented 

 by two commissures covering the fourth ventricle instead of one, the 

 usual number in vertebrata. 



The epiphysis is large in Sauria, while it is rudimental in Ophidia. 

 It extends to the superior cranial wall, and its investing membrane is 

 oppressed, tympanum-like, to the parietal foramen. Its superior expan- 

 sion contains a varying amount of pigment, according to the type, and 

 a layer of cells, forming a cup-like structure with concavity upward. 

 This structure has been supposed to be au organ of special sense allied 

 to sight. It is present in various conditions in most members of the 

 Sauria, but is more or less rudimentary in all. In some forms there 

 is no axial nervous connection with the brain. It is not unlilvely that 

 this is a remnant of an organ of special sense which was functional in 

 some of the extinct Reptilia. There is a very large parietal foramen in 

 the Plesiosauridic, and 1 have found it still larger in the Permian 

 Cotylosaurian family of the Diadectidae. In a number of Eeptilia a 

 similar median body has been discovered close by the epiphysis — the 

 parepipliysis. It resembles the former, but is more rudimental. 



The sacculus endolymphaticus of the internal ear sends upward a 

 branch, which differs in its extent in the different famihes. In the Geck- 

 onidte it extends to the neck and terminates in a sac on either side 

 behind the auditory meatus. This sac is tilled with a mass of lime 

 salt similar to that which composes the otolites. This protuberance on 

 the neck of these reptiles has excited not a little curiosit}', and this 

 feeling is rather stimulated than allayed by the knowledge of its 

 direct connection with the organ of hearing. 



II. SYSTEMATIC RELATIONS. 



From the center of multiplicity of forms of typical Sauria, we can 

 pursue three series — one toward the serpents by Amphislxvna, one to 

 the partially degraded type of the Geckos, and lastly through the 

 highest or pachygloss series, to Ghamcvleon. 



In the first case, the prolonged development of the superior part of 

 the proiitic is followed by a decurving of the parietal bcnxler, the closer 

 attachment of the occipital sclerotome, and shortening of the supratera- 

 poral and paroccipital. Finally the petrosal, with the pieces adjoining 

 anteriorly, begin to restrict a foramen ovale, the orbitosphenoid is 

 developed, and the articular and angular i)ieces of the mandible are 

 represented by but one piece; the columella disappears. In the last 

 direction, the petrosal is not elongate, nor is there any tendency toward 



