Raymond : The Chazy Fokmaiion and its Fauna. 575 



The interior of the dorsal valve frequently shows the muscle scars 

 well. Just behind the center of the valve are two strong elevated 

 scars, the posterior occlusors, and directly in front of them are two 

 depressed scars, the anterior occlusors. iietween these, but a little 

 further from the center, are two depressed scars, the dorsal adjustors. 

 Behind the posterior occlusor scars is a depression which sometimes 

 appears divided by a narrow ridge into two scars. These scars prob- 

 ably belong with the two long lunate vascular scars which are situated 

 outside the occlusors and which reach nearly to the front of the shell. 

 On a few specimens two more pairs of scar-like markings appear — 

 one pair along the posterior margin, and one pair on the lateral mar- 

 gin near the front. 



Locality. — Found at Chazy and on Sloop Island, Valcour Island, 

 New York. 



Rafinesqidna disfans sp. nov. 



Shell small, nearly flat, about three fourths as long as wide. The 

 greatest width is at the hinge. The sides and front are regularly 

 rounded. The surface is marked by eight to twelve prominent striae, 

 between each pair of which are groups of ten to fifteen very fine 

 striffi. There is no other species of Rafinesqtiiiia in the Chazy on 

 which the principal stride are so widely separated, so it can easily be 

 distinguished by that character. 



Locality. — Crown Point and Valcour Island, New York. In the 

 upper Chazy. 



Gastropoda. 



Archinacella f propria sp. nov. 



Shell of medium size, almost circular in outline, depressed, conical, 

 rising to an acute apex which is situated half way between the center 

 and anterior margin. Beak small, scarcely incurved, directed for- 

 ward. Anterior slope concave directly under the beak, l)ut straight 

 for the greater part of the slope. Posterior .slope long and slightly 

 convex. The surface shows a few very fine concentric lines. The 

 greater diameter of the aperture is 1S.5 millimeters, and the lesser 



I7-5- 



Locality. — Fairly common at Crown Point, Yalcour and Chazy, 

 New York. Usually occurs in the Afacliiritcs iiiagni/s division of the 

 Chazy. 



