22 Brachiopoda of the Cincinnati Group. 



apparently wider and shorter than those of the divaricators ; stride and 

 fine granules of the interior as in the other valve. 



Surface of both valves ornamented by numerous, distinct, radiating 

 striae, that usually bifurcate about three times between the beak and 

 free margins; posterior lateral striae so strongly curved that a part of 

 them run out on the hinge line. Numerous, verjuminute, regularly 

 disposed, concentric lines may also be seen by the aid of a magnifier, 

 most distinctly defined in the furrows between the much larger radia- 

 ting stripe ; while a few distant, sub-imbricating, stronger marks of 

 growth are usually seen in adult shells. 



Length of a medium-sized, mature specimen, 0. 60 inch ; breadth, 

 0.75 inch; convexity, 0.25 inch. 



This species is described in the Ohio Paleontolocjy , vol. i., page 109, 

 as 0. emacerata, and fully illustrated on plate 8, figs. 1 a to d, and 

 figs. 2 a to g. 



The typical specimens 2 a to g, are quite common at the quarries in 

 Hamilton, Butler county, associated with 0. ella, 0. belhda, 0. jissi- 

 costa, 0. pUcatella, 0. sinuata, Glyptocrinus decadadylus, and other 

 species indicative of a range from 300 to 400 feet above low water- 

 mark, at Cincinnati. 



It may readily be distinguished from 0. emacerata, for which it has 

 been mistaken, by the following characters, to wit: It is smaller, 

 striffi not so fine, mesial sinus on the dorsal valve and mesial ridge on 

 the ventral valve more distinct and better defined, greatest convexity 

 of the ventral valve more central ; greater cliflference m the size of 

 the anterior and posterior muscular scars of the dorsal valve, and an- 

 terior scars more nearly oval in outline. It has not been found associated 

 with the 0. emacerata, and, so far as known, has a range commencing 

 about fifty feet above the range of the latter, and extending to near 

 the top of the exposure of the Lower Silurian rocks. The largest 

 specimens that I have seen were found near Oxford, in Butler county, 

 Ohio. It is abundant, and has an extensive range. 



Orihis muUisecta— (J aues, 1873), 



Shell small, [sul:)circular, plano-convex, or sometimes concavo-con- 

 vex, hinge line shorter than the greatest breadth of the valves ; 

 valves thin. 



Dorsal valve nearly flat, or having a concentric depression through 

 the middle ; mesial sinus undefined or indistinct ; beak small, not 

 incurved ; area low at the middle, and narrowing oflf to nothing at the 



