SYSTEMATIC REVISION OF THE SUBORDER. 29 



cementum. The solid base to which it is attached is shallow, presenting a smooth 

 surface on the opposite side, which is deeply impressed by a longitudinal groove at 

 one end." 



Original description of species: "The crown is conic, subround in section, and 

 curved backward. There are no cutting edges, and the base is a little flattened in 

 front and behind. Ou each of the faces thus formed, there is an open, shallow groove, 

 sometimes obsolete. There are no other grooves or sculpture on the teeth. * * * 

 One of the specimens displays an extensive pulp cavity." 



Measurements. 



First specimen. Second specimen. 



Diameter of base 0.004 "i- l°°g 0.008 m. short 0.005 "i- 



Length of crown 010 m. .015 m. 



There is so little of this specimen preserved that its exact determina- 

 tion is impossible. It belongs in the family Poliosauridce becaiise of the 

 straight tooth line of the maxillary, the lack of a diastema! notch and the 

 comparatively small size of the enlarged maxillary teeth. It is very 

 possible indeed that it belongs to the genus Poliosaurus. A small vertebra 

 in the collection No. 6578 University of Chicago, Gurle}^, coll., resembles 

 the vertebrae of Theropleura except in its smaller size (fig. 4, plate 6). It 

 perhaps belongs with the jaw. 



Pleuristlon brachycoelous Case (plate i, figs. 14 and 15). 



Second Ann. Rpt. Dept. Geol. and Nat. Hist. Terr. Oklahoma, 1902-3, p. 67. 



Type : Several isolated vertebrae mingled with vertebrae of Lysorophiis tricari- 

 natus Cope. From near Orlando, Oklahoma Territory ; preser\'ed in the Museum 

 of the University of Oklahoma. 



Original description: The vertebrae "are chiefly characterized by the union of 

 the parapophyses and diapophyses in a broad wing-like transverse process, and by the 

 peculiarly broad and large neural canal. The centra are proportionately ver\' broad 

 and the bottom line is devoid of sculpture and with no trace of a keel. The vertebrae 

 are deeply amphicoelous. The neural spine is low and the zygapophyses are relatively 

 large and with flat faces. In some the neural arch seems to be coossified with the 

 centrum and in others it is separated. The transverse process is broader above and 

 becomes narrower below, where it curves forward to touch the anterior edge of the 

 centrum. There is no evidence of the presence of an intercentrum." 



Measurements. 



m. 



Breadth across transverse processes 0.0095 



Height from base of centrum to top of neural spine on 



The position of this genus is uncertain ; it may prove to belong to 

 the same form as Bolosanrus., which is as yet known only by the skull, but 

 its afl&nities seem rather with the Pelycosauria than with the Cotylosauria 

 (plate I, figs. 14 and 15). Specimens of this form occur in several large 

 lots of small bones and fragments from Texas in the American Museum 

 collections. 



