Contributions to Palaeontology. 107 



opposite valves from the St. Croix falls : their relations are not 

 positively known, no entire specimens having been obtained. 



LINGULEPIS PINNAFORMIS. 

 (LINGULA PINNAFORMIS (Owen).) 



PLATE I. FIGS. 14 ft 16 ; AND ? FIGS. 12, 13 & 15. 



Lingula pinnaformis : OwKH, Geological Report of Wisconsin, Iowa and 



Minnesota, pa. 583, PI. 1 B, f. 468. 



: Idem, Rep. of Wis., Vol. i, p. 21, f. 3, and p. 435. 



Shell spatulate, upper part attenuate, acute, slightly trun- 

 cate at the apex; convex in the middle, with the sides, 

 towards the apex, abruptly incurved. Surface marked 

 by lamellose concentric striae ; and, when exfoliated, 

 coarse radiating striae mark the surface of the cast be- 

 low the middle. In some specimens, radiating striae are 

 faintly visible in the shell. 



The ovate valve associated with the spatulate form has 

 a smooth glossy surface, with fine concentric striae ; and, 

 when exfoliated, the surface of the cast is very distinctly 

 striated by fine even or somewhat bifurcating striae. Should 

 this form prove to be distinct from the spatulate one, I 

 propose for it the name Lingulepis matinalis. 



The species is common at the Falls of the St. Croix ; and coarse 

 sandy layers, containing the same fossils, occur near the mouth of 

 the Miniska river- in Minnesota. 



GENUS DISCINA (Lamarck). 



Dr. Owen frequently cites Orbicula among the fossils 

 of the sandstone, and describes Orbicula prima; but the 

 figures given are not satisfactory. These fossils are cited 

 from the St. Croix falls, and upon specimens containing 

 Lingula pinnaformis. So many individuals are indicated 

 (figures 13, 16, IT, 18 £ 19), that it is clearly a common 

 fossil. Among a large collection made at the locality in 



