Raymond: Pelecypoda of Chazy Formation. 333 



Only a single right valve of this species has been found. It is 

 roughly triangular, the beak a little behind the anterior end, and the 

 hinge line short. The anterior end is narrow and rounded, the basal 

 margin long and straight, making an angle of about 45° with the 

 hinge. Posterior margin regularly rounded. Shell only moderately 

 convex, the slope to the posterior margin gradual and that to the 

 front nearly f^at. Surface marked by concentric lines of growth. 

 The length is 15 mm. and height 12.5 mm. This is a larger, more 

 compressed and smoother shell than C. lamellosa, Hudson. 



Locality. — From the Lower Chazy at the ledge in the pasture at 

 Tracy Brook, Chazy, New York. 



6. Cyrtodonta lamellosa Hudson. (Plate XXIX, figure 16.) 



Cyrtodonla? lamellosa Hudson, Report of the New York State Paleontologist for 

 1903 (1904), p. 287, PI. 4, figs. 10-13. 



This is a small shell with moderately convex valves, and very strong 

 lamellae of growth. For a detailed description. Professor Hudson's 

 paper should be consulted. 



7. Cyrtodonta scala Raymond. (Plate XXIX, figure 14.) 

 Cyrtodonta scala R.wmond, Annals Carnegie Museum, Vol. Ill, 1906, p. 578. 



Shell small, strongly convex, the anterior lobe small and depressed. 

 Posterior margin semicircular in outline. Slope from the umbo to 

 the posterior margin more gentle than that to the anterior. One 

 specimen is 11 mm. long and 9 mm. high. 



Locality. — This species has been found only in the trilobite layers 

 at Sloop Bay, Yalcour Island, where it is rare. 



Genus Vanuxemia Billings. 

 8. Vanuxemia limbata Raymond. (Plate XXIX, figures 10, 11.) 



Clenodonta limbata R.\.y.mo.\d, American Journal of Science (Ser. 4), Vol. XX, 1905, 

 P- 371- 



Outline nearly circular, the beak terminal, the shell strongly convex 

 and rounded. Greatest convexity near the middle of the valve; all 

 slopes steep. The cast shows a few faint lines of growth. 



The largest specimen is 10 mm. long and 10 mm. high. A smaller 

 one is 8 mm. in either dimension. 



Locality.- — All the specimens are from the trilobite layers at Sloop 

 Bay, V'alcour Island, New York. 



