Cope.] 44o [Sept. 15, 



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

 Permian Vertebrata publisliod i)reviously* 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^. 



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 vertebrte 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 

 ever}^ respect, so that it is probable that both pubis and ischium are united 

 uudistinguishably 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 vertebme are 

 distinct, and have the usual form seen in Biadectes. 



The two sacral vertebne and the absence of obturator foramen, arc 

 characters of the suborder Pelycosauria in which the latter differs from 

 the DiajnodonUa. 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 Tlieromor- 

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

 to the loss of a loosely articulated basioccipital bone. 



EDAPHOSA.URUS Cope, genus novum. 



Apparently allied to Paiitylas. Temporal fossaj not overroofed ; surfaces of 

 cranial 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 subconical. 



The single spscies of this genus in my pos-iession shows the following 

 characters of systematic importance. An arch extends from tlie parietal 

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

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

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

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

 cess of the sapnio:icipital. A disliuct element connects the basioccipital 

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



♦American Naturalist Feb.. 1881. 

 ;• Vmerlcau Naturalist, 1880, p. 304. 



