BUFFALO SOCIETY OF NATURAL SCIENCES 89 



E 1969 Beak of a right mandible about as large as the cotypes. 



E 1968 A small left mandible (PL 24, fig. 5), which differs from all 

 the preceding in the extreme shortness of the inserted 

 portion, which thins out to a paper edge. This gives the 

 element a peculiar appearance, as if it belonged to a dif- 

 fe,rent genus. However, as the inserted portion in man- 

 dibles of this species is very thin (as may be seen in the 

 type specimens) and is frequently broken and further 

 thinned by attrition, perhaps facilitated by the chemical 

 disintegration of the superficial layer, it is reasonable to 

 suppose that the extreme shortness and thinness of the 

 blade in the present specimen is due to like causes. This 

 " conclusion is supported by the extreme similarity of the 

 functional portion of the element to those described 

 above. The element shows the excavated tritoral 

 region, the beak (which is worn on the outer face), and 

 the front portion of the compressed tritor behind the 

 excavated tritoral portion. In the symphyseal region 

 there are four or five small tritor-like protuberances, one 

 above the other. 



The groove for attachment, along the inferior margin of 

 the element, is well shown. Length, 72 mm.; length of 

 excavated portion of functional margin, 60. 



E 2507 Front half of a right mandible. The symphyseal denticles 

 six or eight in number, are worn down to their bases and 

 the ridge upon which they stood is polished as by func- 

 tional wear. 



E 2508 Front half of a left mandible. The symphyseal denticles, 

 four or five in number, are succeeded below by a polished 

 ridge. 



E 2509 Functional half of a right mandible. The specimen is thin 

 and apparently water- worn. 



E 2592 That this species occurs in the West River Shales, is shown 

 by the impression of a large right mandible, lacking only 

 the beak, in a thin limestone layer, collected by Mr. Bryant 

 a few feet above the Genundewa limestone, at Windom, 



N. Y. 



