OIRTY, l^EW CARBONIFEROUS FOSSILS 223 



Cliothyridina sublamellosa var. atrypoides var. nov. 



Shell rather small, a length of 17 mm. being about the maximum. Length 

 and breadth nearly equal ; sometimes one is observed to be distinctly greater 

 and sometimes the other. The greatest width is usually about midway, but 

 occasionally it is posterior to the middle, the shell having rather prolonged 

 cardinal slopes which join the lateral outline in more or less distinct shoulders. 



The ventral valve is moderately convex with a rather small, not strongly 

 incurved beak. A fairly deep, though undefined, sinus is a constant feature 

 in mature shells. 



The dorsal valve is apt to be gibbous at maturity. A moderately strong 

 fold is present, though seldom conspicuous except along the front margin. 

 Sometimes it is quadrate and comparatively well defined, sometimes rounded 

 and scarcely distinct from the general convexity, very rarely low with a faint 

 median sulcus. 



The surface has the usual spinose lamellae, which are apparently rather 

 crowded. Most of our specimens, however, are exfoliated and the sculpture is 

 obscure. In this condition, the surface is apt to appear nearly smooth ; some- 

 times with more or less crowded but regular concentric ridges ; sometimes 

 with more or less discontinuous radiating costpe and sometimes with both, so 

 that a cancellated effect results. The shell appears to be thick and not pearly. 



Cliothyridina elegans sp. nov. 



Shell rather small, probably not exceeding 17 mm. in width. Regularly, 

 though not strongly, transverse. Greatest width posterior to the middle. 

 Often the hinge is extended, and the greatest width is just in front. Shape 

 lenticular. 



The ventral valve is transversely subelliptical with a small, not very strongly 

 incurved beak. The convexity is low. A rather narrow, shallow, undefined 

 sinus is developed toward the front. 



The dorsal valve is transversely elliptical, gently and regularly convex. In- 

 stead of a fold, there is usually a shallow, linear, median depression, creating 

 with the ventral sinus an emargination of the anterior outline. 



The surface is marked by fine, sublamellose lirje, a few of which are more 

 prominent than others. 



Solenopsis nitida sp. nov. 



Shell of medium size, linguliform. very transverse. Width nearly three 

 times the greatest height. Convexity low. compressed posteriorly. Beak very 

 small and inconspicuous, situated posterior to the front margin by one half or 

 one third the height. Anterior end apparently gaping, especially above. Upper 

 and lower margins subrectilinear and parallel over the median portion, curv- 

 ing together symmetrically toward the posterior extremity, and abruptly 

 rounded at the end. Anterior extremity broadly and regularly rounded. 



Surface marked by concentric stride and very fine concentric lirre. 



