104 NEW YORK STATE MUSEUM 



sometimes more erect, its umbonal convexity less marked. Its sculpture 

 consists of coarse flattened ribs which are more or less irregularly inter- 

 spersed with ribs of smaller size ; on the anterior slope these gradually dis- 

 appear leaving the anterior ear smooth, but on the posterior slope they are 

 continued to the hinge. The posterior wing is cancellated and the cardinal 

 line more strongly striate. The left valve which is less convex than the 

 other has the radial riblets developed only on the median area, both anterior 

 and posterior wings being smooth save on the posterior hinge where there 

 is a cancellated group of three or four strong radii. The variations in the 

 outline of this species reach an extreme in the variety sub recta [pi. 24, 

 fig. 19, 20], which retains the same style of ornament as the foregoing and 

 relative proportions and development of the parts, but is quite erect. This 

 appears to be a persistent feature which we find exemplified in several 

 examples. 



Locality. Edmunds Hill. 



Pterinea brisa Clarke 



I'l.ite 25, figure 10 



Pterinea brisa Clarke. N. Y. State Mus. Bui. 107. 1907. p. 208 



An elongate shell, quite erect, the axis of growth being essentially at 

 right angles to the hinge. The body is produced and moderately expanded ; 

 th • wings distinctly developed but not large, the posterior being narrow, 

 the anterior short and the byssal sinus well defined. The length of the 

 hinge in the specimen before us is 32 mm, the vertical hight 40 mm. The 

 beak is at the anterior third of the hinge. The surface is marked by radial 

 elevated lines with broad, flat interspaces, broken by intercalated lines of 

 minor series. In the umbonal region the lines are close together but 

 they spread outward and the primary interspaces become broad. The 

 body of the valve shows few concentric lines but these are strong on 

 the wings and those on the posterior wing are cancellated by the radii 

 near the hinge. 



Locality. Edmunds Hill. 



Pterinea sp. 

 Type of P t. laevis Goldfs. 



Plate 24, figures 29, 30, 33 



Some incomplete specimens indicate a shell of the general size and pro- 

 portions of tlie forms above described but having a thick shell with smooth 

 or roughly lamellose exterior. 



Localities. Presque Isle stream and Edmunds Hill. 



