GASTROPODA— PALJEACMJEIDJE. 



605 



7. H. cornutiformis Berkey. (Fig. 804, c t d.) Cambric. 

 Slender and high, strongly curved, beak much overhanging. 

 St. Croix formation (Dresbach shales), Minnesota. 



8. H. franconiensis Berkey. (Fig. 804, e,f.) Cambric. 



Fig. 804. a, 6, Hypseloconus recurvus ; c, d, II. cornutiformis ; e, f, H. franconien- 

 sis. (After Berkey, Am. Geol., 21.) 



Curved so as to perform half a volution. 



St. Croix formation (Franconia sandstone) of Minnesota. 



IV. Archinacella Ulrich. 

 Patelliform shells with surface showing only lines of growth, an- 

 terior end generally widest ; apex in front of center and often sub- 

 marginal, generally curved, muscular scars forming a continuous 

 band. Ordovicic. 



9. A. deformata Hall. (Fig. 806.) Ordovicic. 



. Broader proportionally than A. deleta, beak more anterior and 

 overhanging (max. size 11x8 mm.). 



Common throughout the Chazy of the Lake Champlain region. 



Fig. 805. a t 6, Helcionopsis striata; c-e, Archinacella deleta ; f, r, A. simulatrix ; g, 

 A, A. cingulata. (After Ulrich, Pal. Minn.) 



