PERMIAN VERTEBRATES 7 l S 



for one half to three fifths the length of the centrum. Two deep longitu- 

 dinal fossae extend on each side of a median rib of the inferior face ; and 

 they are separated above by a narrower rib from another longitudinal fossa 

 which is below the base of the neural arch. 



MEASUREMENTS. 



C longitudinal - - - .005 5 m 



" Diameter of centrum -j vertical - - - .0038 



( transverse ... .0040 



Length of facet for neurapophysis - -0035 



Width of neural canal - .0020 



This form differs very decidedly from any other in the collection in the 

 prominence of the keel and the lateral ridges ; they, or rather the fossae 

 between them, are developed to an extent that almost destroys the centrum, 

 leaving but a very slender tube surrounding the notochord. A few centra of 

 larger size show strongly developed keels and free neural arches, but much 

 stouter proportions. 



[Nos. 6526 (the type specimen ; it is badly broken), 6527, and 6528.] 



Archaeobelus vellicatus Cope. Plate III, Fig. 1. 



"Species No. 4" Cope, 1877, Proc. Am. Phil. Soc., p. 56. 

 Arcliceobelus vellicatus Cope, 1877, Proc. Am. Phil. Soc, p. 

 192. (Pal. Bull., No. 26.) 



This genus is represented by teeth alone. In his discussion of the form 

 Cope says, in the earlier paper, " there is nothing to prevent their (the teeth) 

 reference to the Lacertilia." The generic description is as follows : "The 

 form is conical, and the surface is not grooved nor furnished with prominent 

 ridges. The interior is hollow, and the walls are composed of a few concentric 

 layers without external enamel or cementum. The solid base to which it is 

 attached is shallow, presenting smooth surface on the opposite side, which is 

 deeply impressed by a longitudinal groove at one end." The specific descrip- 

 tion is given in the earlier paper: "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. On 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 First specimen Second specimen 



" Diameter of base - .oo4 m long .oo8 m short .005 1 " 



First specimen Second specimen 



Length of crown - - - .oio m .015 111 " 



There are several specimens of the isolated teeth described by Cope in 

 the collection, but in addition a considerable portion of a maxillary bone which 



