SYSTEMATIC REVISION OF THE SUBORDER. 37 



Subfamily CLEPSYDROPINAE nov. 



(i) Vertebral spines simple. 



(2) The bottom Hue of the anterior dorsals and posterior lumbars greatly 



shortened. 



(3) Cervicals larger than anterior dorsals. 



(4) Crest of ilium turned to rear and prolonged. 



Genus CLEPSYDROPS Cope. 



Proc. Acad. Nat. Sc. Phila., 1875, p. 407. 



Proc. Am. Phil. Soc, vol. xvii, 1878, pp. 509 and 529. Also Pal. Bull. 29. 



Type: Clepsydrops colletti^ a series of disconnected vertebrae. No. 6530 Univer- 

 sity of Chicago, Gurley, coll.; from Vermilion county, III. Homeotype(C. ;/(7A?/m): A 

 skull and large portion of the vertebral column, imperfect scapulae, pelvis, and humeri, 

 femora, tibia, fibula, and posterior foot and imperfect anterior foot. No. 41 10 Am. 

 Mus. Nat. Hist., Cope, coll.; from Texas. This number includes fragments of at 

 least two individuals, but it seems very probable that the skull belongs to the same 

 individual as the main portion of the spine, which consists of the vertebral column 

 from the fourth (or fifth) presacral to the middle of the tail, with the pelvis complete 

 and the femora of both sides in position with their heads in the acetabula. The 

 femur of the left side has been thrown up and backward until it points in a direction 

 almost diametrically opposite to the natural. The tibia and fibula are attached in 

 position to the distal end. 



Original description of the type, j8j^: "They (the vertebrae) are deeply biconcave, 

 the articular cavities being funnel-shaped and continuous, thus perforating the entire 

 length of the centrum. In a dorsal vertebra the cavities communicate by a very 

 small orifice, while in the posterior the median contraction of the canal is less marked. 

 The posterior cavity is more gradually contracted than the anterior ; in the latter the 

 excavation is, in most of the vertebrae, but slight (except beneath the floor of the 

 neural arch"*, until it falls rather abruptly into the axial perforation. In an (?) anterior 

 dorsal it is as widely excavated at the border as the posterior funnel. Another pecu- 

 liarity is the absence of the processes of the centrum ; and a small capitular articula- 

 tion is seen sessile on the border of the cup of two of the dorsals. 



"The axis* has a singular form, owing to the tubular perforation which continues 

 the posterior excavation to the anterior face of the centnim. There are three articu- 

 lar faces, a larger subround inferior and two smaller superior, which border the neural 

 canal in front and below and are separated from each other and the inferior face by 

 the perforation in question. The anterior face slopes obliquely backwards and down- 

 wards, and is convex in transverse section. There is no facet for the free hypa- 

 pophysis of the odontoid, but it appears that the inferior articular face was applied 

 exclusively to the centrum of the atlas, as in Sphenodon. But the axis differs from 

 that of the latter genus in the absence of a coossified odontoid process. Either that 

 element is entirely wanting or it consists of two pieces, interrupted in the middle 

 by the notochordal foramen, and in correspondence with superior articular facets. 

 There is no true hypajiophysis of the axis, and the only indication of lateral processes 

 is a small articular facet on each side on the lower part of the rim of the posterior 

 funnel. These may have been related to rudimental cervical ribs. The neural arch 

 is broken off. 



*This is the atlas with the intercentrum between it and the axis coossified with it. (PI. 7, figs. 9 and 10.) 



