Cope.] 44:0 [Sept. 15, 



trachys apicalis. The last two were not included in my catalogue of the 

 Permian Vertebrata published previously* in the same year. The present 

 paper adds some important points to this remarkable fauna, and explains 

 the hitherto obscure relations of several genera, 



DIADECTID^E. 



The pelvis and sacrum of a species of this group are preserved in my 

 collection, and they indicate further peculiarities of this group, 



The sacrum consists of two vertebras only, and is thoroughly united 

 with the pelvis by its transverse processes. The latter are decurved on 

 the inner 'side of the iliac bones, and the sutures which distinguish them 

 from the latter and from each other, are not serrate. The inferior arch is 

 robust, but very narrow anteroposteriorly. The acetabulum is entire in 

 every respect, so that it is probable that both pubis and ischium are united 

 undistinguishably in the arch. The pubis is perforated by the usual in- 

 ternal femoral foramen. The posterior edge is grooved, and it might be 

 suspected that this marks the articulation of an ischium. The anterior 

 edge is however grooved in the same way, so that the appearance is rather 

 the position of muscular insertion. The spines of the sacral vertebrae are 

 distinct, and have the usual form seen in Diadectes. 



The two sacral vertebrae and the absence of obturator foramen, are 

 characters of the suborder Pelycosauria in which the latter differs from 

 the Dicynodontia. I am still inclined to question whether the extraordi- 

 nary characters of the cranio-vertebral articulation I have described, jus- 

 tify the separation of the Biadectidce, as a third sub-order of the Theromor- 

 pha, which I have called the Cotylosauria,\ or whether they are not due 

 to the loss of a loosely articulated basioccipital bone. 



EDAPHOSAURUS Cope, genus novum. 



Apparently allied to Pantylus. Temporal fossa? not overroofed; surfaces of 

 crania] bones not sculptured. Mandibular and maxillary teeth subequal. 

 Posterior half of the mandibular ramus expanded inwards and supporting 

 numerous closely arranged teeth. Pterygoid, or perhaps an internal ex- 

 pansion of the malar bones, supporting a dense body of teeth, correspond- 

 ing to those of the lower jaw. Teeth subcorneal. 



The single species of this genus in my possession shows the following 

 characters of systematic importance. An arch extends from the parietal 

 plane posteriorly and downwards to the external base of the quadrate. 

 The specimen is not yet in a condition to show how much of this is parie- 

 tal, and how much squamosal or opisthotic. The proximal half of the 

 posterior part of this arch is a distinct element, perhaps a transverse pro- 

 cess of the supraoccipital. A distinct element connects the basioccipital 

 -on each side with the quadrate. The articular extremity of the latter has 



♦American Naturalist Feb., 1881. 

 + American Naturalist, 1880, p. 304. 



