NATURAL SCIENCES OF PHILADELPHIA. 155 



prominent part being within the middle. Aperture (as inferred from sections 

 of the whorls) transversely subreniform. Septa with a single pointed lobe on 

 each side ; dorsal lobe infundibuliform, the narrow portion being lanceolate ; 

 dorsal saddle broadly and very obtusely rounded ; superior lateral lobe from 

 one-fourth to one-third larger than the dorsal, and having much the same 

 shape, excepting that it is proportionally wider ; inferior lateral lobe consisting 

 merely of a broad rounded sinuosity. (Surface unknown.) 



Should Montfort's name Aganides be retained for this genus, the name of 

 this species would become Aganides compactus. 



Greatest diameter 2-50 inches ; convexity (or breadth of aperture) 1'33 inch ; 

 breadth of umbilicus, about 1\12 inch. 



Locality and position. Coal Measures. Macoupin Co., 111. 



Note in regard to the name "Cincinnati Group," used in the foregoing paper. 



As it is now acknowledged that the rocks along the Hudson river valley, to 

 which the name Hudson River Group had been applied, belong, as long 

 maintained by Dr. Emmons, to a different horizon from the so-called Hudson 

 River rocks of western New York, and the states farther westward, it seems to 

 be an awkward misnomer to continue to apply the name Hudson River Group 

 to these western deposits. Hence it is certainly desirable that this group 

 should receive some appropriate and generally applicable name. Its subdi- 

 visions, it is true, have already received various lithological names, such as 

 " Utica Slate," "Frankfort Slate," "Lorraine Shale," &c. ; but as each of 

 these names will probably be always directly associated, in the minds of 

 geologists, with the particular subdivision to which it was originally applied, 

 while neither of them is applicable to the lithological characters of the whole 

 series, we cannot, without creating confusion, so extend its signification. It 

 has recently been proposed to designate this series as the " Green and Blue 

 Shales and Limestones;" this, however, is not a name, but descriptive 

 phrase, and has the disadvantage of being based upon lithological characters 

 not everywhere characteristic of these beds. 



In view of all the facts, we have concluded to propose the name Cincinnati 

 Group (which will be adopted in the forthcoming reports of the Illinois Geo- 

 logical Survey) for this series. This name possesses the advantage of being 

 equally applicable to rocks of any color or composition, while it carries the 

 mind to a well-known locality, where the formation referred to is extensively 

 developed, and its fossils so abundant that they have been thence widely 

 distributed, both in this country and Europe. Consequently, geologists will 

 everywhere at once understand to what particular horizon of the Lower Silu- 

 rian this name refers. 



Descriptions of New Crinoidea, &c, from the Carboniferous Rocks of Illinois 

 and some of the adjoining States. 



BY F. B. MEEK AND A. H. WORTHEN. 



Genus POTERIOCRINUS, Miller, 1821. 



POTERIOCRINUS InDIANKNSIS, M. & W. 



Body rather deeply cup-shaped or truncato obconic. Base basin-shaped, 

 comparatively rather broadly truncated below by the columnar facet. Basal 

 pieces well developed, pentagonal, about one-third wider than high. Sub- 

 radials large, three pentagonal, and two on the anal side hexagonal, there being 

 no defined angle at the middle of the under side of any of these plates. First 

 radial pieces about half as large as the subradials, wider than long, rounded 

 on the outside, and nearly pentagonal, or with one or both of the superior 



1865.] 



