DESCRIPTIONS 



Of New Species of Fossils from the Upper Helderberg, 

 Hamilton and Chemung groups ; with observations upon 

 previously described species. 



[ Continued from page 94 of the preceding Report.] 



PRODUCTUS DUMOSUS ( n. s.). 



Shell subqvoid, arcuate. Ventral valve broadly gibbous, with 

 beak incurved. Surface marked by strong radiating ridges, 

 which gradually become stronger, and terminate abruptly in 

 long tubular spines rising almost vertically from the surface : 

 interstitial ridges of the same character mark the surface in 

 successive ranges, so as to give a tolerably regular series of 

 spines, of which there are as many as ten ranges. The sur- 

 face is otherwise marked by fine concentric undulating striae. 

 Dorsal valve unknown. 



This species has a length of one inch, with a width of three-fourths 

 of an inch : the height or depth of the ventral valve is more than half 

 an inch. It is quite distinct from any other species known to me in 

 strata of -this age. 



Geological formation and locality. In shales of the Hamilton group : 

 near Canandaigua lake. 



ATHYRIS ANGELICA (n. s.). 



Shell ovoid, gibbous, elongate ; width and length about as six 

 to seven, or twelve to fifteen. Ventral valve most convex 

 above the middle, marked throughout its length by a strongly 

 defined and abruptly depressed mesial sinus, which becomes 

 somewhat suddenly expanded on the lower third of the shell : 

 sides of the shell gibbous, and abruptly curving to the mar- 

 gins ; beak extended and incurved. Dorsal valve much shorter 



