No. 2328. PLEISTOCENE VERTEBRATES IN UNITED STATES— HAY. 101 



transverse, 8 mm. There is merely a suggestion of a groove on the 

 hinder face. 



PLATYGONUS TETRAGONUS? (Cope). 



Plate 4, figs. 16-17. 



In the Cavetown collection is part of an inferior right canine 

 (Cat. No. 9188) which differs from any found at either Cavetown or 

 Corriganville, near Cumberland. It appears to conform most closely 

 to Cope's description of his Mylohyus tetvagonus;^ but the tooth, 

 as did Cope's species, belongs evidently to Platygonus. The frag- 

 ment here described and illustrated (pi. 4, figs. 16, 17) lacks both 

 the base and the summit. It is 37 mm. long. Near- the lower frac- 

 ture the width is 12 mm.; the thickness, 7.2 mm.; that is, at this 

 level the thickness is 0.6 of the breadth. In the canine described by 

 Cope^ the dimensions were 10 mm. and 6 mm. 



Cope found that the lower canine of his species had the angle 

 between the hinder face and the inner one truncated by a narrow 

 plane which followed the length of the tooth. Such a plane appears 

 to be represented in the tooth at hand. The hinder face is flat at the 

 lower end of the fragment, slightly concave at the upper. It is 

 bounded on each side by a narrow ridge. Mesiad of the inner bound- 

 ing ridge is a surface flat at the upper end, slightly concave at the 

 lower. Mesially this surface is bounded by a ridge on the inner 

 face. The surface referred to appears to meet the requirements of 

 Cope's description. 



The inner face (pi. 4, fig. 16) of the specimen at hand is finely 

 wrinkled in front of the ridge referred to. The outer face is more 

 coarsely sculptured. Figure 17 of the plate cited shows a section 

 of the tooth at the lower fracture. So far as represented, the tooth 

 shows no wear, and it is traversed by the yet open pulp cavity. 



PLATYGONUS VETUS7 Leidy. 



Plate 4, figs. 18-19. 



This species appears to be represented by a fragment of the left 

 ramus of the lower jaw (Cat. No. 9189) bearing the first and second 

 true molars (pi. 4, fig. 18). The first molar is pretty well worn 

 down, but the second only moderately so. These are referred to 

 Platygonus vetus rather than to Gidley's P. cumberlandensis, be- 

 cause of the greater size of the lower teeth of the Cavetown spe<n- 

 men. The following measurements are taken from the specimen from 

 Cavetown, from Leidy's measurements of the type of P. vetus,^ and 

 from the type of P. cumbeo'landensis. 



1 Journ. Acad. Nat. Sci., Phila., vol. 11, 1899, p. 260, pi. 21, fig. 3. 



' Idem., p. 260. 



^Ann. Rep. Geol. Surv. Penn. for 1887, p. 14. 



