PALEONTOLOGY. 489 



MOELUSCA. 



LAMELLIBRANCHIATA. 



Genus AVICULOPECTEN McCoy. 



Avictclopecten inter lineat us. 



PLATE XII, figs. 10 and 11. 

 Aiiculopecten interlineatus M. and W., Proc. Acad. Nat. Sci. Phila., 1860, p. 454; 

 Geol. Rept. 111., vol. 3, p. 229, pi. 26, fig. 7. 



Shell sniall, subcircular in outline, hinge-line straight, nearly as long as the 

 width of the shell below, and with sharp angular aurieulations. Valves very gently 

 convex. Surface of the left valves marked by fine, even, lamellose, concentric 

 stria; several of which are more strongly and highly elevated, forming varices at 

 regularly increasing distances. Right valve also marked by similar fine striae, but 

 with the varices very indistincly marked, or barely perceptible under a lens. 



The species is a very strongly marked one, and very characteristic 

 of the Coal Measures. Mr. Meek describes indications of faint radii 

 between the varices on the examples from Illinois, but which do not 

 appear on specimens from Ohio so far as observed. The right valve fig- 

 ured occurs close by the other, and is evidently of the same individual ; 

 the features are very similar, differing only in the absence of the strong 

 concentric varices. 



Formation and Locality. — In a thin layer of chert of the Coal 

 Measures, near the farm of Mrs. Banks, Falls township, Hocking county. 

 Ohio. 



GASTEROPDA. 



Genus NATICOPSIS McCoy. 

 Naticopsis Ortoni. 

 PLATE XII, figs. 12 and 13. 

 Naticopsis Ortoni Whitf., Aim. N. Y. Acad. Sci., 1885. p. 230. 



Shell small, with a somewhat depressed conical spire, which forms an angle of 

 about 105 degrees, and the two and a half to three volutions are obliquely flattened 

 on their upper side, in the direction of the spire ; the outer one being marked just 

 below the suture by a barely perceptible concave channel of considerable width, 

 which produces a very slight angularity of the upper part of the volution. Suture- 

 line slightly grooved. Lower side of the volution rounded; umbilicus closed; callus 

 slight; aperture obliquely ovate at the outer margin, but rounded within from the 

 excessive thickening of the shell. Surface of the shell marked by fine, rather equal 

 and somewhat regular transverse striae of growth, most distinctly marked on the 

 lower half of the volution. On the outer half of the last volution, there occur lines 

 of nodes, very faintly indicated, having a direction opposite to the growth-lines, and 

 becoming faintly and finally imperceptible toward the lower side. 



The species resembles N. nana M. and W. (Geol. Rept. 111., vol iii, 

 p. 365, pi. 32, fig. 4), in size and general form, but differs from it in the 

 greater flattening of the volution in the direction of the spire and in the 

 faintly nodose surface. 



Formation and Locality. — In a thin cherty band of the Coal Measures 

 in the railroad cutting at Mrs. Banks' farm, Falls township, Hocking 

 county, Ohio. 



