yeir ^Species iif Fossih from Ohio. 213 



U'hu tjpecies recoguized and described as occurring in the shules 

 above referred to are as follows; most of them being previously 

 known. The species marked as new are described below. 



Linyulu Munni, Hall. 

 Lingula Ligea, Hall. ? 

 Discina inlnata. Hall. 

 JJiscinuLodensis, Hall. 

 Uhoietes scitula, Hall. 

 (Jkunetes reverm, n. sp. 

 Spirifera Main, Billings' s]). 

 Leiorlijjnclms Umitaris, Vanuxem's sp. 

 Avict(lopecfe?i equilatera, Hall's sp. 

 Fteruiea simiUs, n. sp. 



Clioiietes reverj»a, u. sp, 



Pill. O., Vol. Ill, Plate 7, Figs. Sandy. 



Sboll of about a medium size, semicircular iu outline, with a long straight 

 hiuge-line exceeding the width of the shell below. Valves resupinate, or 

 reversed in their curvature ; the ventral being very slightly convex in the 

 earlier stages of growth, and subsequent^ recurved so as to appear con- 

 cave ; the entire detiection from a plane being very little, so that the general 

 appearance of this valve may be said to be nearly flat. Area linear. Hinge- 

 line ornamented by four long, very slender spines on each side of the centre, 

 Avhich are projected from the hinge-line at an angle of about 65 degrees, 

 measured on the outside, or 115 degrees as counted on the inside of the 

 spine. Surface of the ventral valve marked by exceedingly fine striae, 

 which are slightly alternating in size ; there being from two to five finer 

 ones between the coarser kind. Interior of the valve characterized by fine 

 pustules, arranged in indistinct lines, presenting the usual characteristics of 

 the genus. Dorsal valve not positively known ; but there is associated with 

 it, in the same layers, a slightly convex valve with similar stritB, but more 

 distinctly alternating, which may possibly represent this valve. Its form 

 is similar, and the convexity correspondingly great. 



TIlis species is peculiar in its resupinate character, so far as 



thor says : "In the State of Ohio similar conditions may he infen-ed. from the fact that certain 

 species of Hamilton fossils are puhlished in the Ohio Geol. Rept. as from the Corniferous 

 group." By reference to the 28th Vol. of the Proc. of the Am. Association for the Advance- 

 ment of Science, p. 297, it will be seen that, at the Saratoga meeting of the Association, I read 

 a paper on the discovery of the Marcellus Shale in Ohio : in which it is stated that the rocks 

 above that horizon (the Marcellus) would necessarily be Hamilton. This was iu August, 1&79. 

 The volume above-mentioned is dated, in the letter of transmissal, Dec. 15th, 1879. 



