IN THE EEPTILIA. 13 



broad single arch remains single, but becomes more and more slender and can be 

 interrupted. Plesiosauria, Theromora, Mammalia, Squamata (Lacertilia, Pythono- 

 morpha, Ophidia). II. In the broad single arch appears another opening, the infra- 

 temporal fossa, forming an upper and lower arch which connects the orbit with the 

 quadrate ; E,h jnchocephalia ; the whole Archosaurian branch (Crocodilia, Dinosau- 

 ria, Pterosauria) ; birds." Dr. Baur then proceeds to identify the postorbital arch of 

 the Lacertiha with the quadratojugal or zygomatic arch, expressing the belief that 

 the ancestors of that order never possessed any other quadratojugal arch, and that 

 the present elevated position of the arch in the Lacertilia is due to reduction at the 

 inferior border. Thus the supratemporal of the lizards (squamosal Auct.) would be 

 the equivalent of the quadratojugal of Sphenodon. 



In the endeavor to reach a definite conclusion regarding these questions, I have 

 examined my specimens of the Eeptilia of the Permian formation, as being most 

 likely to furnish essential facts. I now give the results of this examination. 



I. The Reptilia of the Peemian. 



I have well-preserved crania which display sutures of the following species : 

 CMlonyx rapidens Cope ; Pantylus cordatus Cope ; Parioticlius megcdops Cope ; 

 ^dapJiosaurus pogomas Cope; Clepsy drops natalis Cope; Naosaurus claviger Cope; 

 Diopeus leptocephalus Cope. 



The genera Chilonyx, Pantylus and Pariotichus have the temporal fossae entirely 

 roofed over, thus belonging to the Cotylosauria,* to which must be probably referred 

 the genus Pariosaurus Owen, of the South African Karoo formation, and the Phane- 

 rosaurus of the German Permian. The other genera, excepting Diopeus, belong 

 to the Pelycosauria, which is probably the same as the Theriodonta of Owen. 



CniLONrxf agrees with the Stegocephalia, and with other Diadectidse in pos- 

 sessing a distinct os intercalare. The component elements of the cranial roof are 

 equal in number and similar in position to those of the Stegocephalian skull, except 

 that the supraniastoid extends between the parietal and intercalare to the posterior 

 border of the cranial table (Fig. 2, 8m.) ; and the supraoccipital does not extend onto 

 the superior face of the skull, except as a narrow border. The quadrate bone is 

 directed forwards instead of posteriorly, which causes an anteroposterior abbreviation 

 of the supratemporal and squamosal elements. The elements of the temporal roof 



* Cope. American Naturalist, 1880, p. 304 ; October, 1889. Pariosauria Seelej'. Philos. Transac, Loudon, 1889, 

 p. 292. 



fCope, Proceed. Amer. Philos. Soc, 1883, p. 631. 



