328 PROCEEDINGS OF THE ACADEMY OF 



something less than a right angle to the hinge, to the anterior 

 basal margin, the anterior side, thus circumscribed, being some- 

 what flattened, and, as seen from the front, presenting a cordate 

 outline. Surface ornamented with small, very regular, simple 

 concentric costa?, that seem to be obsolete on the anterior and 

 posterior portions of the valves. (Hinge and interior unknown.) 



Length, parallel to the cardinal margin, about 0.45 inch; height, 

 at right angles to hinge, to the tops of the beaks, about 0.45 inch; 

 length, measuring from the points of the beaks obliquely to the 

 posterior basal extremity, 0.57 inch ; convexitj^, 0.39 inch, 



I have referred this shell provisionally to Cardio'mor2oha, rather 

 because it seems to present at least as many external points of 

 resemblance to some species of that genus as to any known palaeo- 

 zoic group, than from any strong impression that it reall}^ belongs 

 to the same. In some respects, its general physiognomy suggests 

 affinities to the group of secondary shells for which Prof. Agassiz 

 proposed the name Ceromya, though I do not think it would fall 

 into that genus. When all of its characters can be determined, 

 it will probabl}' be found to belong to an undescribed genus. If 

 so, I would propose for the group the name Ceromyopsis^ from its 

 resemblance to some species of Ceromya. 



Although presenting some points of resemblance to the last- 

 described species, this shell maj- be distinguished at a glance, not 

 only by its small distinct concentric costje, but by its much less 

 sharply carinated beaks, and more rounded posterior umbonal 

 slopes, as well as by its flattened anterior side; this flattening 

 imparts a subangular character to its anterior umbonal slopes, 

 not seen in the last. 



Locality and 2Wsition. — Cincinnati group of the Lower Silurian 

 in same bed as the last at Cincinnati, Ohio. Mr. Dj'er's collec- 

 tion. 



GASTEROPODA. 



MACROCHEILUS KLIPPARTI, Meek. 

 Shell a,ttaining a large size, elongate-fusiform, the length being 

 sometimes from two and a half to three times the breadth ; spire 

 pointed at the apex, forming about half the entire length, with 

 its lateral slopes concave above and convex below ; volutions six 

 to eight or nine, the upper five or six being very compactl3' coiled, 

 and forming comparatively but a small part of the entire shell, 



[March 19, 



I 



