708 E. C. CASE 



studded with teeth, which are not in contact with each other. Their size 

 increases from one side of the bone to the other, and still more, from one 

 extremity to the other. The crowns are swollen at the nearly sessile base, 

 and contract rapidly to a conical and unsymmetrical apex. One side of the 

 latter is slightly concave below the apex. The surface is shiny and distinctly 

 grooved. Fractured crowns do not display any central cavity." 



The present specimen is rather oval, one side showing a perfect convex 

 outline and the other with three straight edges at large angles to each other. 

 The whole plate is convex on the toothed side and concave below. The 

 angulated border is thickened and roughened and the rounded border thin. 

 The surface is covered with teeth, larger in the middle and on the thickened 

 border than on the other edges. The plate is .oi58 m long and .0114™ wide. 



[Nos.6511 (Cope's type) and 6512.] 



£ricotus heteroclitus. Plate I, Figs. 12a, 12b, 12c, \2d, 13, 14. 

 Cricotus heteroclitus Cope, 1875, Proc. Phil. Acad. Nat. Sc, 



p. 405. 

 Cricotus heteroclitus Cope, 1877, Proc. Am. Phil. Soc, p. 64. 

 Cricotus discophorus Cope, 1877, Proc. Am. Phil. Soc, p. 186. 



(Pal. Bull., No. 26.) 

 Cricotus heteroclitus Cope, 1878, Proc. Am. Phil. Soc, p. 



522. (Pal. Bull., No. 29.) 



The genus was founded on some intercentra which were regarded as cen- 

 tra of the caudal region; it was not until 1878 that the true nature of the 

 intercentra was made out. With the intercentra were a few other bones 

 doubtfully referred to the same genus. That portion of the original descrip- 

 tion which is applicable to the bones as intercentra is as follows : " The caudal 

 vertebra (intercentrum) best preserved is stout, discoidal in form, and deeper 

 than wide. It resembles in form that of an herbivorous dinosaurian, but 

 differs otherwise. The articular faces are deeply concave, the posterior most 

 strikingly so ; and the middle is occupied by a large foramen, whose diameter 

 is about equal to that of the centrum on each side of it. The lateral borders 

 of the posterior articular face are expanded backwards, and articulate with a 

 bevel of the corresponding edge of the anterior articular extremity. In this 

 way the vertebra combines the mechanical relations of the biconcave with 

 opisthoccelian structures. These neural arches (hsemapophyses) are narrow 

 and directed backwards ; their bases are firmly coossified with the centrum." 

 .... " On the inferior (superior) surface of the centrum (intercentrum) two 



shallow pits occupy considerable space " It will be noticed that the 



describer had the intercentrum inverted ; this fact was later understood by him- 

 self and certain drawings corrected. The structure of the skull and other 



