of Emmons, in Washington County, N. Y. 191 



Ventral valve convex, most elevated about one-fourth the 

 distance from the beak to the anterior margin ; beak small and 

 incurved to the margin of the medium sized area ; the surface 

 of the area and the foramen have not been observed ; mesial 

 sinus broad and shallow, it is marked by a low median rib 

 and, laterally, by two costse on each side, a third appearing 

 just outside the sinus. 



The dorsal valve, associated in the same hand specimen of 

 limestone, is slightly more convex ; frontal margin with a 

 rather deep sinuosity to receive the projection of the ventral 

 valve ; median fold broad and but slightly elevated, marked 

 by two or three low costse ; the beak appears in the broken 

 specimen in the collection to be scarcely elevated above the 

 surface of the shell, and to terminate at the cardinal margin ; 

 area unknown. 



The surface of both valves is marked by fine concentric lines 

 of growth, and low, rounded costae, varying in number from 

 six to seven, as in the specimens figured, to twelve or fourteen 

 in other specimens. 



In the broad costae and the general aspect of the shell this 

 species is unlike any known to me from the Cambrian. 



Formation and localities.— Cambrian. Limestones, interbedded 

 in the shaly Taconic slates, one and one-half miles south of 

 Salem ; one mile south of Shushan, and near Rock Hill school- 

 house (No. 8), Greenwich, Washington County, N. Y. 



Hyolithellus micatsts var. rugosa, n. var. 

 Plate I, fig. 10. 



This name is proposed for a variety of Hyolithellus micans 

 that has well-marked concentric ridges with longitudinal striag 

 between them. The substance of the shell appears to be simi- 

 lar to that of H. micans. (See Bull. 30, U. S. Geol. Survey, p. 

 142.) 



Formation and localities.— Cambrian. Limestones, interbedded 

 in the shaly Taconic slates on the roadside just west of Low 

 Hampton crossing of the Poultney river ; lowest fossiliferous 

 horizon on D. W. Reid's farm, and on hill back of Reid's farm- 

 house, one and one-half miles west of North Greenwich ; two 

 miles south of North Granville ; and in the north part of 

 Easton, about one mile south of the village of Greenwich, 

 Washington County, N. Y. 



Modiolopsis ?? prisca, n. sp. 

 Plate I. fig. 19. 



The only specimen of the species known to me is the cast of 

 a right (?) valve, 2 mm in length. It is transversely oval in out- 



