OF DENISON UNIVERSITY. -^3 



Productus dclorosus. Win., is apparently a synonym for P. truncatus, 

 H., and has not yet been certainly identified within our limits. 



Typical ventral valves of P. shumardianus are frequent in the 

 sandy parts of conglomerate I, though never found much above this 

 horizon. A dorsal valve apparently of this species was found in the 

 nodules at the foot of the exposure at Moot's run, at least 50 feet be- 

 low the horizon of conglomerate I. I quote Hall's description. 



" Shell concavo-convex, sub-hemispherical, wider than long ; 

 hinge-line nearly or quite e(iualling and sometimes greater than the 

 shell below. Ventral valve very convex, gibbous in the middle and 

 on the umbo, which is abruptly narrowed toward the beak, and the 

 apex curv-ed over the hinge line ; the sides abruptly depressed toward 

 the cardinal extremities, which are flattened and more or less auricu- 

 late. In one specimen observed, the apex is minutely truncate, and 

 there is a barelv perceptible line at the junction of the two valves, 

 which indicate an area. Dorsal valve concave, often corresponding 

 essentially with the ventral valve^ but sometimes nearly flat in the up- 

 per and central portions and abruptly deflected toward the margin. 

 Surface of the ventral valve marked by intermittent radiating ridges, 

 gradually rising from the surface and terminating below in elongate 

 spines ; while upon the upper part of the shell, about the umbo, there 

 are scarcely perceptible elevations of the surface above the base of the 

 spines. * ^' ^-^ The entire surface is marked by close concentric 

 undulating striae." 



The cardinal process of the dorsal valve is bifurcate. I'igs. 6, 6a, 

 6b and 11, of Plate XII, illustrate various conditions of this species, 

 Fig. 6 especially resembling P. spinulicostatus. 



[ProdiictiLS concentricus, " 1 



(Plate VI, Fig. 16.) 



(=: P. shumardiana, H. ?) 



The identification of this dorsal valve was suggested by Prof. A. 

 Winchell, but it is made with some hesitation, as the specimen wa.s 

 found associated with P. shumardianus as above indicated. In mark- 

 ings, both concentric and pustulose, the valve agrees belter with that 

 species from which it seems to difTer somewhat in form. Nodules, 

 foot of exposure at Moot's run. 



