PALEONTOLOGY. 44S 



Genus CHONETES Fischer. 



Chonetes scitula. 



PI.A.TE VII, fig. 10. 

 Chonetes scitula Hall, Pal. N. Y., vol. 4, pt. 1, p. 130, pi. 21, fig. 4. 



Shell small and semicircular in outline, or in some cases semi-ovate being a 

 little more than half of a circle. Hinge-line as long or a little longer than the shell 

 below, and but slightly mucronate at the extremities. Ventral valve nearly equally 

 convex or a little depressed just within the cardinal extremities. Dorsal valve flat- 

 tened or slightly concave. Surface marked with about sixty, fine, even strise in the 

 larger specimens, as counted on the ventral valve, and the hinge-line bears three 

 short spines on each side of the beak. 



The specimens being in limestone are all much exfoliated, so that 

 the surface strise are not distinctly shown toward the cardinal borders. 

 The shells are perhaps a little longer than the more typical forms of C. 

 scitula as they occur in the Hamilton shales near Cayuga Lake, N. Y., 

 and are somewhat intermediate in this respect between those and C. Yan- 

 delli Hall, from the hydraulic limestones from near Louisville, Ky. 



Formation and Locality. — In thin-bedded bituminous limestones of 

 the Marcellus shale, above the "Bone-bed" at Smith and Price's quarries, 

 near Columbus, Ohio. 



Chonetes reversa. 



PtATE VII, figs. 8 and 9. 

 Chonetes reversa Whitf., Ann. N. Y. Acad. Sci., 1882, 213. 



Shell of -about medium size, semicircular in outline, with a long, straight hinge- 

 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 subsequently recurved so as to appear concave ; the entire deflection 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, which 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 

 strise, 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, ar- 

 ranged in indistinct lines, presenting the usual characteristics of the genus. Dor- 

 sal valve not positively known ; but there is associated with it, in the same layers, a 

 slightly convex valve with similar strise, but more distinctly alternating, which may 

 possibly represent this valve. Its form is similar, and the convexity correspond- 

 ingly great. . 



This species is peculiar in its resupinate character, so far as the genus 

 is known in American Devonian rocks, and this character, together with 

 its form, its fine strise, and its nearly erect slender spines, will readily 

 distinguish it from any other species. The dorsal valve above spoken of 

 was at first supposed to be the young of Strophodonta perplana Conrad's 

 sp., but the similarity in size and character of striae to this species ren- 

 ders it doubtful > 



Formation and Locality. — In thin-bedded bituminous limestone, from 

 above the " Bone-bed " at Smith and Price's quarries, near Columbus, Ohio. 



