Raymond: Pelecypoda of Chazy Formation. 339 



17. Modiolopsis exanimis sp. nov. (Plate XXX, figure 11.) 



This species is very like the preceding, but is so much shorter and 

 higher that it cannot be united with it. 



Locality. — A rare species in the Upper Chazy on Valcour Island, 

 New York. 



18. Modiolopsis parviuscula Billings. (Plate XXX, figures 14, ? 15, 



16.) 



Modiolopsis parviuscula Billings, Canadian Naturalist and Geologist, Vol. IV, 

 1859, p. 446; Whiteaves, Ottawa Naturalist, Vol. XXII, 1908, p. 106, pi. 

 Ill, figs. I, ? 2. 



This species which was described by Billings in a single sentence of 

 less than two lines, and not figured, must rest on the single Chazy 

 specimen now remaining at Ottawa. This specimen is on a bit of 

 fine-grained, dirty-looking limestone from Cornwall, Ontario, and in 

 the same bit of matrix there are several fragments of Camarotcechia 

 plena. The Modiolopsis is apparently crushed and flattened, and 

 shows nothing more than the general outline. The distinctive feature 

 about the specimen is that the posterior basal angle projects beyond 

 the upper angle or any part of the posterior end of the shell. In this 

 feature the shell is like Modiolopsis nwdiolaris, to which Billings 

 compared it, and by the same feature it may be distinguished from 

 all other species of Modiolopsis in the Chazy or Aylmer formations. 



Description. 



The type, a right valve, is small, with short hinge and semicircular 

 anterior end. The ventral margin is nearly straight, and much longer 

 than the hinge. The posterior margin is oblique, the posterior angle 

 abruptly rounded, while the posterior dorsal angle is very obtuse. 

 A low broad ridge extends from the umbo to the lower posterior 

 angle, and the shell slopes gently in all directions from it. The surface 

 is marked by numerous concentric lines of growth. 



Locality. — From the Upper Chazy at Cornwall, Ontario. 



What appears to be the same species occurs in the lower part of 

 the Pamelia formation at Aylmer, and a very good specimen, collected 

 by T. W. E. Sowter at that locality, is figured (PI. XXX, figs. 15, 16). 



