12 POSTEKIOR CRANIAL AKCHES 



Mammalia, thus coinciding with the opinion as to the homologies of that arch held 

 by Kallmann, Owen and Peters, and as described by Giinther in Sphenodon. On 

 further study of the Permian reptiles contained in my collection, and comparison of 

 them with recent orders, I am more than ever convinced of the correctness of this 

 view, and I propose in the present paper to show the evidence on which it rests. 

 It follows, moreover, that if this interpretation be correct, the bone ordinarily called 

 quadratojugal must be called the squamosal or zygomatic, while the bone to which 

 that name is ordinarily applied must receive another name. The element immedi- 

 ately above the true squamosal, which roofs the temporal fossa in the Stegocephali 

 and Cotylosauria, is the supratemporal of Owen,* first described by him among 

 reptiles in Ichthyosaurus. The element immediately above the supratemporal in the 

 Stegocephali, Cotylosauria and Ichthyopterygia is the mastoid of Cuvier and Owen. 

 As it is probably not homologous with the part of the Mammalian skull called by that 

 name, some other one must be found for it. The numerous names given to bones in 

 this region of the skull all apply to the squamosal or supratemporal, so I propose to 

 name this one the supraTnastoid. 



Posterior to the supramastoid in the Stegocephalian and in some of the Cotylo- 

 saurian skulls, is an element which frequently projects in an angle in the posterior 

 outline, and which corresponds with the element present in the fishes, which Cuvier 

 termed the intercalare. The relation of this piece to the paroccipital of certain rep- 

 tiles remains to be ascertained. 



It is evident that the correct classification and phylogeny of the Reptilia will 

 not be completed without the determination of the homologies of these segments, 

 and the homologies of the arches to which they contribute. In the endeavor to 

 accomplish this analysis I have been much aided by a suggestion made by Dr. 

 George Baur, which has been fertile of valuable results. In a recent papert he says : 

 " In the oldest Batrachia, the Stegocephalia, we find a continuous dermal covering of 

 the upper and lateral paits of the skull • ■» * ^ the number of these dermal ossi- 

 fications is nearly constant, -sfr * * The complete covering of the skull is for the 

 first time interrupted in the Ichthyosauria and AetosauriaJ by the appearance of a 

 supratemporal fossa, which develops between the parietal, squamosal and the upper 

 posterior border of the orbit. The bony arch below the supratemporal fossa, which 

 connects the orbit with the quadrate, is now afiected in two different ways : I. The 



*Suprasquairiosal of Owen is the same; see Palieontology, pp. 168, 174, 198. Seeley uses the term supratyni- 

 panic for the same. 



t American Journal of Morphology, 1889, p. 471. 

 if Or Pseudosuchia. 



