270 PROCEEDINGS OF THE ACADEMY OF 



This species seems to be much like Pleuratomaria serrilimba, of Phillips, 

 judging from his figure, (Geol. Yorks. 11, pi. xv. fig. 30) ; but it is utterly im- 

 possible to make satisfactory comparisons with species so briefly described aud 

 poorly figured, without having access to authentic specimens. 



Locality and position. Macoupen County, 111. Lower Coal Measures. 



Orthonema conica, II. & W. 



Shell elongate conical, thin. Volutions (in adult shells) about nine, flattened 

 nearly on a line with the slope of the spire, or but slightly convex ; lower 

 ones sometimes a little projecting at their lower margins immediately above 

 the suture ; last one distinctly angular around the middle, and but modera'ely 

 produced below the angle, where it is a little convex. Umbilical region not 

 indented. Suture generally well defined between the lower whorls, aud merely 

 linear above. Aperture rhombic subquadrate. Surface showing, under a 

 magnifier, small, very slightly oblique lines of growth, which are sometimes 

 crossed on the middle of the flattened outer slope of the body whorl, by very 

 faint traces of two revolving ridges, and below the angle, on the under side. 

 by traces of another revolving ridge. 



Length, 0-70 inch ; breadth, 0-30 inch ; apical angle a little convex on its 

 slopes, divergence about 30. 



This species will be readily distinguished from our O. Salteri, from the 

 same locality and position, by its larger size, smaller number of whorls, 

 greater apical angle, and particularly by never having the two linear revolv- 

 ing ridges just below the suture, so characteristic of that species. As men- 

 tioned in the description, it sometimes, though rarely, shows traces of two 

 very obscure revolving ridges on the flattened part of the body whorl, but 

 these are midway between its principal angle and the suture, while those on 

 O. Salteri are always very distinct, and placed just below the suture. The 

 principal angle on the body whorl of O. Salteri is also much more distinct, 

 being a true carina. 



From the several species of Pohjphemopsis of our coal-measures, such as our 

 P. inornata, P. peraci/ta, &c, which it somewhat resembles, this species will 

 be distinguished by its angular body whorl ; and particularly by not having 

 this whorl produced below, and its columella curved outwards and trunca- 

 ted, so as to produce the peculiar effuse character of the base of the aperture 

 seen in that genus. 



Locality and position. Hodge's Creek, Macoupen County. 111. Lower Coal 

 Measures. 



TROCHITA ? CARBONARIA, M. &. "W. 



Shell small, depressed trochiform, or broadly conical, about twice as wide 

 as high, circular in outline as seen from above ; periphery alate and very 

 sharp, not serrate or crenate ; apex central, mammillated ; volutions about 

 five, flattened or a little concave in the middle ; suture merely represented by 

 a nearly obsolete line scarcely visible without the aid of a magnifier ; aper- 

 ture unknown ; umbilicus small, infundibuliform. Surface smooth on the 

 upper whorls, but showing moderately distinct, extremely oblique lines of 

 growth on the last turn. 



Breadth, 035 inch ; height, 0-17 inch ; apical angle about 105. 



This little shell resembles quite nearly Trochella prisca, of McCoy, from the 

 Carboniferous limestone of Ireland ; from which it differs in its much smaller 

 size, and moderately distinct lines of growth. So far as we know, it is the 

 first shell of this type ever found in our American Palaeozoic rocks. Its alate 

 margin seems to project as a sharp rim around the periphery, and the general 

 aspect of the shell is very like that of the genus J'horus, though we have been 

 unable to see any indications of foreign bodies being attached to the margin. 

 We are not sure, however, but we would be nearer right in calling it Phorus 

 carbonarius, or Onustus carbonarius. 



[July, 



