27O NEW YORK STATE MUSEUM 



Enkeberg). These toque-shaped shells are however subequivalve, and, 

 while they are arched and mitriform and concentrically rugose like the 

 New York species, the latter is thus far chiefly represented in our collec- 

 tions by specimens of the left or arched valve only. Such right valves as 

 may be looked on as appertaining to these are depressed convex or fiat. 



Kochia ungula sp. nov. 



Plate 13, fig. 1-7 



These shells are valves with highly overarched umbo, narrow, produced 

 and incurved beak and relatively short body with wing and ear suppressed. 

 Shells of this character but of widely different size occur in the shales of 

 the Chautauqua subprovince. They may be more precisely described as 

 follows. Marginal outline subcircular or subrhomboidal. Anterior margin 

 inflected beneath the beak, making a rounded angle of less than 90 with 

 the basal margin ; the latter transverse. Postbasal angle 90 . Posterior 

 margin direct, postcardinal oblique and moderately long. Contour capuli- 

 form ; umbo produced beyond the hinge line, strongly arched downward 

 and beak incurved and recurved. Over the main body of the valve the 

 umbo is delimited by abrupt lateral slopes on both sides. The posterior 

 slope is broader and gently concave, the anterior is directed inward from 

 edge of the umbonal slope. Surface over the umbonal region and all the 

 early parts of the shell with broad obscure concentric wrinkles. The mark- 

 ings become finer about the margin where these wrinkles are obsolescent. 

 Of 10 specimens of this species observed, the majority are of small size, and 

 nearly all are left valves. 



The specimens regarded as right valves of this species are somewhat 

 obliquely subrhomboidal in outline with beak in front of the middle. The 

 umbonal region is gently convex, and the surface over the pallial region, 

 in front, behind and below is broadly depressed and gently concave about 

 the basal margin. Length and width nearly equal. Surface covered with 

 concentric striae, which may take on the form of low plications. 



Observations. Kochia capuliformis Koch is the only other 



