56 Brackiopoda of the Cincinnati Gmip. 



The proportion as to length, breadth, and convexity, is not uniform 

 by any means. Length of one specimen, 0.84 inch ; width, 1.44 inches; 

 convexity, 0.40 inch. Length of another, 0.76 inch ; width, 1.20 

 inches ; convexity, 0.40 inch. Specimens are found varying from less 

 than one fourth the size of these to one fourth larger. 



This species abounds in the upper part of the Cincinnati Group 

 (from 500 to 800 feet above low water-mark, at Cincinnati), at almost 

 every locality. And it also extends through the entire group, unless 

 the form described by Mr. James as S. gibbosa, vol. i., p. 333, of this 

 Journal, October, 1874, is to be regarded as a distinct species or variety. 

 I think, however, that Mr. James' form is at least a good variety. 



For StrojjJiomena squamida (James), see vol. i., page 335, of this 

 Journal, October, 1874. This form is regarded by collectors, generally, 

 as the young of S. alternata, but I am inclined to think with Mr. 

 James, that it is a distinct species. 



For Strojihomena declivis (James), see vol. i., page 240, of this 

 Journal, July, 1874. 



Genus Leptena — (Dalman, 1828). 



Semi-circular, depressed, entering valve concave, the other evenly 

 convex from the hinge line, which is as long as the shell is wide; 

 cardinal area distinct, slightly rhomboidal, about equally formed of 

 both valves ; the convex or receiving valve has a triangular opening 

 nearly filled by the projecting angle of a rhomboidal, two or four- 

 lobed boss at the beak of the entering valve, leaving only a minute 

 perforation, separated by a small pseudo-deltidium from the apex; 

 punctured structure minute, often indistinct or obsolete ; internal sur- 

 face rough, with little points ; entering valve Avith a small, bifid tooth 

 at the beak, in front of which are two small diverging ridges, between 

 which is a moderate longitudinal sejitum. Some species show a 

 minute tubular foramen at the apex of the beak. 



There is but one species generally recognized (L. sericea) in the 

 Cincinnati Group, though Mr. James has characterized one of the 

 forms as distinct from the others, under the name L. aspera, vol. i., 

 page 151, of this Journal, Aj)ril, 1874. 



