450 GEOLOGY OF OHIO. 



berg limestones of New York few representatives of this species have 

 been recognized, and those present a coarser, ruder form than the Hamil- 

 ton group specimens ; and specimens from the limestones from below the 

 " Bone-bed," near Columbus, are 'not uncommon, but are very large, very 

 coarse, and rude in character, having but a distant resemblance to the 

 typical forms of the species. These I strongly suspect are properly a 

 distinct species, but the examples thus far obtained have been of so im- 

 perfect a character as not to furnish characters sufficiently marked to 

 determine this question. 



Formation and Locality. — In rocks above the " Bone-bed ; " horizon 

 known as the " Petroleum Rock," in Tully township, Marion county, Ohio, 

 The specimen figured is from the State collection at Columbus, and was 

 collected by Rev. Mr. Herzer. 



Genus ACTINODESMA Sandb. 

 Actinodesma subrecta. 

 Plate VII, fig. 20. 

 Actinodesma subrecta Whitf., Ann. N. Y. Acad. Sci., 1882, p. 215. 



Shell of moderate size; the body of the shell, exclusive of the wings and 

 hinge extensions, ovate in outline, and slighly oblique to the cardinal line. Hinge- 

 line extended in the form of strong articulations or wings on the sides of the shell; 

 the upper margin straight, or a little declining on each side of the beak ; anterior 

 wing short, triangular and divided from the body of the shell by a deep and wide 

 sub-triangular notch ; posterior side long and sub-mucronate at the extremity, 

 three to three and a half times long as the anterior side, and its area much greater, 

 extending along the, body of the valve to nearly half its length from the beak. 

 Body of the left valve more than moderately convex, and strongly arcuate or bent 

 between the beak and base of the shell ; so that when placed on a flat surface, the 

 margin, especially on the posterior side, would be much elevated above the plane. 

 Beak of the valve large, sub-tumid, and slightly extended above the cardinal line. 

 Ivength of the body of the shell, from the cardinal line to the base, about one-fifth 

 greater than across it in the opposite direction. Anterior border broadly rounded,' 

 the basal margin more sharply so, with a slight angularity at its junction with the 

 nearly direct posterior border. Surface of the shell marked by irregular, concentric, 

 strongly lamellose lines, resembling those of the Byster. Right valve not yet 

 observed from Ohio. 



The species is allied to A. recta — Avictda recta Conrad, but is shorter, 

 more ventricose on the left side, more arcuate or bent, and with 

 less extended wings. It is not an uncommon species in the solt 

 shales of the Hamilton group of New York, where it is readily 

 recognized from A. recta by the above mentioned characters. The A. 

 recta is most common in the arenaceous beds of eastern New York, while 

 this is the prevailing form among the soft shales further west. The right 

 valve is there recognized as being shorter than the left, concave instead 

 of convex, with an appressed beak or umbo not extending beyond the 

 cardinal line, and the valve is much thinner in its substance, 



Formation and Locality. — In layers of brownish limestone above the 

 "Bone-bed," at Fishinger's mill, Franklin County, Ohio. Collected by 

 the Hyatt brothers, of the S L ate University at Columbus. 



