Beyricliia striato-marginatiis. 233 



The interior of tlie valves is characterized by a line of crenulations 

 on tlie inner border of the rim, as well as upon the outer border. The 

 crenulations on the inner border are the most prominent, and from 

 whicli the rim is depressed to the outer boi'der. 



Length, about -g^ths of an inch; width, about ^%ths of an inch. 



It may readily be distinguished from the Beyrichia tumifrons, Avhich 

 it most nearly resembles, by the single depression across the surface, 

 instead of two sulci. It dilfers also in having a wider rim and being 

 smaller in size. 



I found this species on the top of Vine street hill, in Cincinnati, 

 about 430 fbet above low water-mark. Not observed elsewhere. This 

 may be, however, on account of its being so small that it is scarcely 

 visible to the naked eye. 



The specific name is given in honor of Mr. Charles Dury, of Cin- 

 cinnati, a devoted naturalist and artist, whose handiwork in taxidermy 

 and in the preparation of insects ornaments the finest museums in 

 the city, and whose mind is broad enough to lead him to embellish 

 his own cabinet with the fossils of the Cincinnati Group. 



Beyrichia striato-mavginatus — (S. A. Millee). 



Fig, 26. — Beyrichia st nalo-marginatus, magnified about 20 diameters. 



Shell small, semi-elliptical; dorsal margin straight, rounded at both 

 ends ; basal margin elliptical. Valves strongly convex, with a single 

 depression extending from the middle of the dorsal margin, at right 

 angles, about half the breadth of the shell. Border one thind the 

 width of the shell, and finely striated or lined from the shell outward. 



Length about -g%th inch, and width about ^^^th inch; convexity 

 nearly as great as the width. 



I found this sj^ecies in the upper fifty feet of the Cincinpati Group, 

 about fifty miles west of Cincinnati, and about three miles south of 

 Osgood, Indiana. 



