Cope.] 514: [April 5, 



iscbia in Clepsydrops natalis, are of a size appropriate to the present spe- 

 cies. They include both the ilia, ischia and pubes in one mass, forming a 

 compressed boat-shaped body with a prominent inferior keel. 



The prominent character which distinguishes this species is the shortness 

 of the ischiatic symphysis. Its extent anterior to the acetabulum is only 

 one-half the diameter of the latter, while it equals that diameter in the 

 G. gigas. It follows from this, that the crest arising from the anterior 

 border nf the acetabulum is abruptly decurved a little anterior to the latter, 

 and descends to the inferior keel at a very steep angle. At its point of de- 

 curvature is a prominent tuberosity. The front of the symphysis pubis 

 presents an obtuse keel, which terminates short of the apex. The inferior 

 border of the acetabulum is not sharply defined, except at its posterior 

 portion. 



Measurements. M. 



Total length 260 



Length from posterior border of acetabulum forwards. . .148 



Long diameter of acetabulum 095 



Total vertical diameter to superior border of acetabulum .135 



Length of anterior symphysis 085 



From the same locality as the last species. 



DlMETRODON RECTIPOE.MIS. Sp. nOV. 



This species is represented by portions of the vertebral columns of three 

 individuals at least. Its size exceeds considerably that of the Clepsydrops 

 natalis, equaling that of the C. [? Embolophorus) limbatus Cope. Of the 

 latter species I possess numerous vertebrae, and they all differ in a marked 

 manner from the present species. 



In Dimetrodon rectiformis, the depth of the centra does not exceed the 

 length. The margins of the articular faces are not twisted, and the articu- 

 lar faces of the zygapophyses are horizontal. The opposite is the case in 

 the G. limbatus. The spaces for the intercentra are small ; they are large 

 in G. limbatus. The vertebra described as typical is a posterior dorsal. 

 Here the diapophyses is nearly sessile, and below the line connecting the 

 zygapophyses. Its costal articular surface is narrowed downwards and 

 forwards, almost reaching the recurved border of the anterior face. The 

 neural spine is much elevated, and the sides of the centrum are concave. 

 The inferior articular borders are connected by an acute nearly horizontal 

 edged keel. 



Measurements. M. 



( antero-posterior .031 



Diameter of centrum •< transverse 034 



(vertical ». . . .026 



Expanse of posterior zygapophyses ..... 030 



Length of base of neural spine 025 



From the same region as the other species here described. 



