264 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57, 



MATHERELLA SARATOGENSIS (Walcott) 

 Plate 41, figs. 18-21 



Billingsia saratogensis Walcott, 1886, Bull. U. S. Geol. Surv., No. 30, p. 21. 



(Name given in list of species, but no description or figure.) 

 Trochus ? saratogensis Walcott, 1890, Proc. U. S. Nat. Mus., Vol. 13, pp. 



268-269, pi. 20, fig. 3. (Original description as below.) 

 Billingsia saratogensis Walcott, 1891, Bull. U. S. Geol. Surv., No. 81, p. 346. 



(Copy of the first reference.) 



Shell trochi forme, sinistral, broadly conical with about four 

 slightly convex whorls ; base concave ; umbilical surface sloping 

 inward from the angle produced by its union with the outer curvature 

 of the body whorl ; umbilicus rounded and of medium size ; aperture 

 obliquely subelliptical ; periphery unknown. Surface marked by a 

 few fine striae of growth. 



This shell is not a true Trochus, and in the photographic plate 

 illustrating the Potsdam fauna of Saratoga County, New York, that 

 I prepared in 1885 (page 252) , it bears the name Billingsia saratogen- 

 sis. This generic name was used in lists of species in 1886,^ but no 

 publication of the description of the genus has yet appeared. The 

 name Billingsia having been preoccupied (page 263) the species was 

 in 1890 provisionally referred to Trochus until further comparisons 

 could be made. 



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 PALJEACM^A Hall and Whitfield 



Palaacmcca Hall and Whitfield, 1873, Twenty-third Ann. Rept. New York 

 State Mus. Nat. Hist., p. 242. (Description of genus.) 



PALJEACMJEA TYPICA Hall and Whitfield 



Plate 43, figs. I and 2 



Palceacmcea typica Hall and Whitfield, 1873, Twenty-third Ann. Rept. New 

 York State Mus. Nat. Hist., p. 242, pi. 2, figs. 4 and 5. (Description 

 of species as below, figures 4 and 5 being reproduced in this paper as 

 figures I and 2 of plate 43.) 



The original description is as follows : 



Shell patelliform, broadly oval in outline, with a depressed conical exterior, 

 and a pointed subcentral apex, situated three-sevenths of the greatest length 

 from one extremity. Surface of the shell marked by several strong folds or 

 undulations parallel to the lines of growth. 



^ Bull. U. S. Geol. Survey, No. 30, 1886, pp. 5, 21, 60, and 62. 



