578 AxxALs OF THE ('arxegie Museum. 



Locality. — Division 2 of the Chazy limestone, Valcour Island, New 

 York. 



]Vhiteavsia ? expansa sp. nov. 



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

 running diagonally from the beak to the lower angle of the posterior 

 margin. 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 

 strong on the umbonal portion of the shell. 



An average specimen is 19 millimeters long and 14 millimeters 

 high. 



Locality. — In the middle Chazy at Valcour Island, New York. 



Cyrtoilo/ita scala sp. nov. 



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

 Posterior margin semicircular. Slope from the umbo to the i)Osterior 

 margin more gentle than that to the anterior edge. One specimen 

 has a length of 1 1 millimeters and a height of 9 millimeters. 



Locality. — In the black limestone of the middle Chazy at Valcour 

 Island, New York. 



JVliiteavsia ? uiiilatitni sp. nov. 



Shell rather small for the genus, robust, the upper and lower mar- 

 gins subparallel. Beak elevated, small. A broad, shallow depression 

 extends from the umbo to the basal margin, giving the shell a flat- 

 tened appearance. Posterior margin regularly rounded ; anterior 

 margin almost straight, meeting the hinge at almost a right angle. 

 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. Length 

 of one specimen, 25 millimeters, height 12.5 millimeters. 



Locality. — The middle Chazy on Valcour Island, New York. 



Biblio(;raphy. 



In the following pages an attempt has been made to cite all of the 

 more important papers on the Chazy formation or its fauna. It has 

 not been the intention to give abstracts of the papers, but where they 

 contain valuable information not brought out elsewhere in this article, 



