24 



THE HISTORY OF THE PELYCOSAUEIA, WTTH 



vertebrae and an intereentrum, and two other portions of dorsal vertebrae of limbolo- 

 phorus dolloverianus Cope. 



The next paper to be mentioned is by Prof, ("ope, 25 " On the Homology of the 

 Posterior Cranial Arches in the Reptilia," published in April, 1892. 



Clepsydrops leptocephalus Cope is made the type of a new genus, Diopeus Cope. 

 The following species have well-preserved crania which display sutures: Chilonyx rapi- 

 dens Cope ; Pantylus cordatus Cope ; Pariotichus meyalops Cope ; Edaphosau/rus pogonius 

 Cope; Clepsydrops natalis Cope ; Naosaurus claviger Cope ; Diopeus leptocephalus Cope. 



" The genera Chilonyx, Panlylus and Pariotichus have the temporal fossa} entirely 

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

 genus Pareiasaurus Owen, of the South African Karoo formation, and the I'hunerosaurus 

 of the German Permian. The other genera, excepting Diopeus, belong to the Pely- 

 co&auria, which is probably the same as the Theriodontia of Owen. 



" Chilonyx agrees with the Stenocephalia and with other Diadeetidw in possessing a 

 distinct os intercalare [epiotic aut.; par occipital plate, Baur, 26 1889 ; 08 tabulare or tabular 

 bone, Cope, 27 1894] . The component elements of the cranial roof are equal in number and 

 similar in position to those of the Stegocephalian skull, except that the supramastoid 

 [squamosal] extends between the parietal and intercalare [paroccipital plate] to the 

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

 on to the superior lace of the skull, except as a narrow border. The quadrate bone is 

 directed forwards instead of posteriorly, which causes an antero-posterior abbreviation of 

 the supratemporal [prosquamosal] and squamosal elements. The elements of the temporal 

 roof are not exclusively tegumentary, but are identical in character with the bones of the 

 brain case, and the sutures are visible on the under as well as the upper side 



"Pantylus agrees with Chilonyx in the composition of its cranial roof with the excep- 

 tion that the suspensorium is vertical and is not directed forwards" (Fig. 4, PI. 1). 



" Pariotichus Cope agrees in the main with Chilonyx, butthe supraoccipital is divided 

 medially and is reflected on to the superior face of the skull as in Hlegocephali. The inter- 

 calare [paroccipital plate] is reduced to a small element, of which a small part appears 

 on the superior face of the skull immediately behind the exterior part of the supra- 

 mastoid " [squamosal] (Fig. 3, PI. I). 



Then it passes to the Theriodontia (Pelycosauria). 



In "Naosaurus Cope (Fig. 7, PI. TT), the orbit is in the posterior part of the skull and 

 (he muzzle is greatly elevated and compressed [?]. The zygomatic (quadratojugal) is 

 greatly decurved posteriorly and the supratemporal [prosquamosal] is accordingly 

 decurved also. The postfrontal (Fig. 7a) is a narrow bone, wider than long, and it has 

 connection with the frontal, parietal and postorbital only. The postorbital is an L-shaped 



