Description of Some Xeir Species of Fossils. 97. 



Upper valve depressed convex, with the apex placed about three 

 fourths of the semi-diameter fi-om the posterior margin. Lower valve 

 flat or slightly convex, with the apex ceutral; foraminal impression or 

 slit narrow and well defined, extending from the center of the valve 

 about two thirds of the distance to the margin. 



Surface of both vah^es marked by very fine and sharp concentric 

 striae, which are somewhat irregular, since a number of them are 

 branched, two or more running into one. All the striae show through 

 the shell on the interior. No radiating lines were observed. 



Diameter of lower valve, 1 c. m.; length of foraminal slit, 3 m. m. ; 

 width of same, .5 m. m. ; height of upper valve, 2 m. m. 



This shell resembles Discina circe, Billings, but difters from that 

 form in having the lower valve quite flat, the apex of the upper valve 

 nearer the center, and in being much more finely striated, twenty-six 

 of the concentric striae occupying the space of 4 m. m., while in that 

 species there are not half that number in the same space. 



Locality and Position. — Found in the lower part of the Cincinnati 

 Group, back of Covington, Ky., at an elevation of one hundred and 

 fifty feet above low water mark at Cincinnati, Ohio. 

 I 



Discina sublamellosa, u. sp. (Plate IV., fig. 11.) 



Shell above the medium size, extremely thin, nearl}^ circular, or 

 sometimes broadl}^ oval, the length ranging in that case to one fourth 

 greater than the breadth. 



Upper valve much depressed, with the apex varj-ing in its position, 

 from nearh' marginal, to one sixth the length of the valve from the 

 posterior margin ; a low and broad mesial ridge is observed, running 

 in a.curved direction, from near the anterior margin to the apex, the 

 line being deflected toward the left lateral margin. 



Lower valve not observed. 



Surface of dorsal valve, ornamented by rather strong, lamellose, con- 

 centric striaj, with from six to seven in the space of five millemeters; 

 some of the specimens also show a few heavy, radiating lines, placed 

 on the low mesial ridge. 



Length of medium sized specimen, 13 m. m. ; width a little less; the 

 convexity can not be exactly ascertained, since all the specimens 

 examined are somewhat compressed, but I do not doubt, that it is less 

 than 3 m. m. 



Discina circe, of Billings, is remotely related to this form, but the 

 nearly marginal apex, the strong and few concentric lines, and the 

 heav}' radiating striie, as well as the mesial ridge in D. sublamellosa, 

 will serve to distinguish them. 



Locality and Position. — In the Cincinnati Group, near Covington, 



