Descriptions of Xeu- Geneva and Species of Fossils. S) 



undoubtedly of the age of the Trenton ; and also, we believe, that the 

 Hlaek River limestone crops out at the Kentuekv River, below irigh 

 Bridge, Frankfort, and possibl}^ at several other localities. The strata 

 exposed at Cincinnati, from low water mark in the Ohio River to about 

 seventy-five feet above that horizon, and which are considered by 

 nearly all the geologists at Cincinnati to be referable to the Utica 

 shale, differ from the strata above and below them lithologically, as 

 well as in the fossils they contain. At least twenty-six species occur 

 in them that are not known to have been found in the strata referred 

 to the Trenton Group, nor in those of the Hudson River Group. These 

 species are : Buthrotrephis raniulosa., Miller ; Lockeia siliquaria. 

 James ; Chceietes hriai'cus, Nicholson ; Choitetes calicula, James; 

 Dendrocrinus dyeri. Meek : Groptoiithus tenuis(?). Poi-tlock : Di- 

 cranograj^tus ramosus. Hall ; Diplograptus ichitjieldi., Hall ; Diplo- 

 gvaptus spinulostis{?)^Y{?i\\ ; Leptoboluslepis^HoW ; 3Iodiolopsis cin- 

 cinnafiensis, Hall and Whitfield ; Leperditia byrnesi. Miller; eight 

 species described in this paper : Heterocrinus geniculatus^ Dendro- 

 crinus{?) curtiis, Palceaste)- Jinei, Leptcena plicatella, CyrtoUtes nitidu- 

 fns, Lepet'ditia radiata, L. hivertex, L. unicornis, and six undeter- 

 mined species; two crinoids, probabl}' new, a Leperditia^ a grapto- 

 lite, a fucoid, and an uudescribed species of Crustacean, allied to 

 Enoploura. Although there is some intermingling of the species occur- 

 ring in this western exposure of the Lower Silurian, on the whole, we be- 

 lieve that there are sufficient reasons for reinstating the old terms by 

 which its subdivisions w'ere known. 



Genus Leperditia (Roualt). 

 Lepekditia radiata, n. sp. (Plate VIL, figs. 2, 2a, 2^. ) 



lY.iy .—Radlatus, radiating.] 



Length, 0.2 ; breadth, 0.17 inch. 



Carapace from sub-quadrate to sub-reniform ; dorsal margin straight, 

 nearly as long as the length of the valve ; anterior and posterior ends 

 equal, either slightl}' truncate, or broadh' rounded ; ventral margin 

 convex. Valves depressed convex, with a slighth' defined, rather 

 broad marginal rim. Tubercle situated near the middle of the valve, 

 small, sub-oval, and not very prominent ; substance of tubercle very 

 thin, rarely preserved, the position of the tubercle usually being 

 marked by a perforation in the valve. Surface minutel}- striate ; stria* 

 radiating from four or five points on the valve ; the striae composing 

 the central group are the strongest, and radiate from the tubercle. In 

 .some specimens, the strise show through the valve on the interior; in 



