OF DENISON UNIVERSITY. 37 



Chotietcfi pitlchdla, ^Vin. 

 (Plate III, Fig. 14.) 



"Shell small, semi-circular; hinge almost equalling the greatest 

 width, rectangular at the extremeties, furnished with two or three stout 

 hollow spines on each side of the beak, one projecting from the hinge 

 extremity, and diverging at an angle of about 22° with the hinge-line 

 — the second half way to the beak and diverging at an angle of 45°, 

 each of these spines having a length equal to half the hinge line. 

 Ventral valve, exclusive of the flattened hinge angles, spherically con- 

 vex; internal median ridge extending to the middle of the valve. 

 Surface with about 54 feeble, rounded ribs, often nearly obsolete on 

 the hinge angles; these are crossed by numerous microscopic, concen- 

 tric striae; the grooves beneath the ribs are acute and bear a few spin- 

 ous projections near the shell margin. Dorsal valve nearly flat, gen- 

 erally a little concave near the margin, marked, like its fellow, with 

 radiating lines, and often a few concentric folds. .-Vrea very narrow. 

 equally excavated in both valves." 



Our specimens are 7 mm. wide and about 5 mm. long. Kindly 

 identified by Prof. Winchell. Specimens believed to have come from 

 the free-stone of middle Waverly, Granville, O. 



Heinipronites crenistr'ui, I'h'l- 

 (Plates V, Fig. 14; III, 24; Plate VI, Fig. 8; Plate IX, Fig. 21.) 



The great variability of the American members of Hemiproniles 

 makes any attempt to restrict the limits of species very difficult— for 

 us, impossible. The figures indicate the extremes of the series abun- 

 dant in the middle Waverly. 



This widely distributed species occurs in all the strata containing 

 numerous fossils. The largest specimens .seen come from the same 

 horizon as Spirifer marionensis, i)robably 60 feet below congl. I, though 

 these are less than half the size of the largest figured by Davidson. 

 <Sup. plate XXXVI.) These are very transverse and the stri;L' arc 

 very fine and frecpicntly irregular. The ventral valve is only moder- 

 ately convex. (Dorsal valve 58 mm. wide. 30 mm. high) about 13 

 strict in 5 mm. (near the margin.) In the shale below congl. I, spcci- 



