Raymond: Pelecypoda of Chazy Formation. 337 



One specimen is 6.5 mm. long and 5 mm. high, while a second is 

 6 mm. long and 4 mm. high. 



Locality. — Found at the base of the Upper Chazy on Sloop Island, 

 east of Valcour Island, N. Y. Also at the same horizon on V^alcour 

 Island and at Chazy, New York. Also in the Upper Chazy at the 

 Mingan Islands, Canada. 



Family Modiolopsid^ Fischer. 



Genus Whiteavsia Ulrich. 



13. Whiteavsia? undata Raymond. (Plate XXX, figures 23, 24.) 

 Whiteavsia} undata Raymond, Annals Carnegie Museum, Vol. Ill, 1906, p. 578. 



Shell rather small, robust, the upper and lower margins sub-parallel. 

 Beak elevated, incurved, small. A broad, shallow depression extends 

 from the umbo to the basal margin, giving the shell a flattened appear- 

 ance. Anterior margin nearly straight, meeting the hinge in almost 

 a right angle. Posterior margin rounded. From the umbo an 

 oblique ridge extends to the lower anterior angle of the shell, and the 

 slope from this ridge to the front is steep. 



The length is 25 mm. and the height 12.5 mm. 



Locality. — A very rare shell in the trilobite layers. Sloop Bay, 

 Valcour Island, New York. 



14. Whiteavsia ? expansa Raymond. (Plate XXX, figure 20.) 

 Whiteavsia} expansa Raymond, Annals Carnegie Museum, Yo\. Ill, 1906, p. 578. 



Shell oval in outline, only moderately convex, with a strong ridge 

 running diagonally from the beak to the lower posterior angle. The 

 slope from this ridge to the hinge and posterior margin is abrupt 

 and rounded. To the basal margin the slope is gradual and almost 

 flat. The internal cast shows a small but distinct anterior muscle 

 scar and strong concentric growth lines, which are especially prominent 

 on the umbonal portion of the shell. 



An average specimen is 14 mm. high and 19 mm. long. 



Locality. — A rare species in the trilobite layers of the Middle Chazy 

 at Valcour Island, New York. 



Genus Endodesma. 



15. Endodesma tranceps Raymond. (Plate XXX, figures 17-19.) 

 Cyrtodoftta tranceps Raymond, American Journal of Science (Ser. 4), Vol. XX, 

 1905. P- 372. 



