160 rBOCEEDINGS OF THE NATIONAL MUSEUM. vol.xxii. 



Class P»ELEOiri>ODA.. 

 Family NUCULID^ Gray. 



CTENODONTA SUBNASUTA Ulrich ? 



(Plate XIII, figs. 4-6.) 



Ctenodonta suinasuta Ulrich, Geol. Minn., Ill, Pt. 2, 1894, p. 585, pi. xlii, figs. 

 34-36. 



There are two examples of this species, and these appear to agree 

 best with Minnesota specimens of C. subnasuta. They were sent to 

 Mr. E. O. Ulrich for direct comparison with his types. He writes: 



You can not be far wrong if you identify these specimens with C. subnasuia. Still, 

 there is some doiibt as to their identity. The Arctic specimens are larger than the 

 types, and relatively a little more elongate, while the basal outline is scarcely as 

 convex, and the umboues not so full and evenly rounded. Finally, the smaller end, 

 which I am now somewhat inclined to regard as the anterior, is relatively wider in 

 your shells. I may add that the larger sijecimea indicates a thinner hinge plate 

 than in the types, so that, after all, these specimens may belong to a distinct species. 

 Typical C. snlmasuta occur in the Trenton of Manitoba. 



Collectors.— J . N. Carpender and A. H. White. Cat. No. 28163, 



U.S.N.M. 



CTENODONTA CARPENDERI, new species. 

 (Plate XIII, figs. 1-3.) 



This is the most abundant pelecypod from Silliman's Fossil Mount 

 and appears to be closely related to G. cuneiformis Ulrich.' It dif- 

 fers, however, in various details, particularly in always being consid- 

 erably larger. C. carpenderi has also the general aspect of small 

 specimens of G. nasuta, but differs in the straight hinge line, especially 

 that of the posterior end, which terminates abruptly into the regularly 

 convex outline of this portion of the shell. 



Mr. E. O. Ulrich, to whom several examples were sent, wrote as 

 follows : 



These specimens are closely related to C. cuneiformis Ulrich. The types of that 

 species are much smaller, with the narrower end relatively shorter and the constric- 

 tion more distinct. Good specific difl'erences are found in the postcardinal region 

 (i. e., assuming that the wider end is posterior). Here the Arctic species is more 

 impressed, causing the umbonal ridge to be much more prominent, the postcardinal 

 slopes wider and concave instead of flat. Just behind the beaks there is a triangu- 

 lar shaped area (ligamental probably) which is wanting in C. cuneiformis. 



Named after Mr. J. N. Carpender, of New Brunswick, New Jersey, 

 who made the most extensive collection of fossils at the head of Fro- 

 bisher Bay. 



Collectors.— S. N. Carpender, A. H. White, and A. Y. Shaw. Cat. 

 No. 28104, U.S.N.M. Other specimens collected by Mr. E. W. Porter 

 are now in the American Museum of Natural History. 



iGeol. Minn., Ill, Pt. 2, 1894, p. 597, pi. xlii, figs. 31-33. 



