NO. 9 NEW YORK POTSDAM-HOYT FAUNA 265 



Formation and locality. — Upper Cambrian: (77) Potsdam sand- 

 stone near the water below the falls at the high bridge, and also at 

 several horizons in the section, the highest point being 70-75 feet 

 (21.3-22.9 m.) above the water, ia Ausable Chasm, Essex County; 

 and in Potsdam sandstone at the north end of the town of Whitehall, 

 Washington County ; both in New York. 



Genus MATTHEVIA Walcott 



Matthevia Walcott, 1885, American Journ. Sci., 3d sen, Vol. 30, p. 17. 



(Genus described and discussed.) 

 Matthevia Walcott, 1886, Bull. U. S. Geol. Surv., No. 30, pp. 223-224. (A 



copy of the previous description.) 



MATTHEVIA VARIABILIS Walcott 

 Plate 42, figs. 1-15 



Matthevia variabilis Walcott, 1885, Amer. Journ. Sci., 3d ser., Vol. 30, p. 18, 

 and figs. 1-6, p. 20. (Species described and illustrated.) 



Matthevia variabilis Walcott, 1886, Bull. U. S. Geol. Surv., No. 30, pp. 224- 

 225, pi. 32, figs. 1-12, pi. 23, figs. I, la-f. (Described as in 1885, with added 

 illustrations.) 



This species is described very fully in Bulletin 30, of the U. S. 

 Geological Survey. 



Formation and locality. — Upper Cambrian: (76) Arenaceous 

 Hoyt limestone at Hoyts quarry, 4 miles (6.4 km.) west of Saratoga 

 Springs, Saratoga County, New York. 



Genus HYOLITHES Eichwald 

 HYOLITHES GIBBOSUS Hall and Whitfield 



Plate 43, figs. 5 and 6 



HyoUthes gibbosus Hall and Whitfield, 1873, Tvi^enty-third Ann. Rept. 

 New York State Cab. Nat. Hist., p. 242, pi. 11, figs. 1-3. (Description of 

 species as below, figures i and 2 of plate 11 being reproduced in this 

 paper as figures 5 and 6 of plate 43.) 



The original description is as follows : 



Shell elongate conical, gradually tapering to an obtuse point, and slightly 

 curving; very depressed, convex on the ventral side, and highly convex and 

 gibbous on the dorsal, the sides being nearly vertical for a short distance from 

 their junction with the ventral margin. Aperture rather more than semicir- 

 cular; the lip on the ventral portion moderately projecting. 



This species resembles HyoUthes (Theca) primordialis Hall, from the 

 Potsdam sandstones of Wisconsin, but differs in being much more convex on 

 the dorsal side, and in the less projecting lip of the ventral side of the aperture. 

 The outlines given in figure 3 show the relative convexity of the two species, 

 the outer dorsal line being that of H. gibbosus, and the inner of T. primordialis. 



