1 82 NEW YORK STATE MUSEUM 



Genus strophonella Hall 

 [Ety. : arpofos, turned around] 

 (1879. A r . Y. state mus. nat. hist., 26th an. frep't, p. 153; Hall & 

 Clarke. 1892. Pal. N. Y. v. 8, pt 1, p. 290) 



Shells with the form and structure of Stropheodonta, but 

 with the relative convexity of the valves reversed. 



Strophonella striata Hall (Fig. 87) Leptaena striata 

 Hall (1852. Pal. N. Y. 2:259, pi- 53, % 7) 



Distinguishing characters. Semielliptic, almost 



llljl flat, hinge line equal to or a little longer than width 



of shell; fine, rounded, radiating surface striae, 



which increase by implantation; fine concentric 



Fig. 87 Strophonella 

 striata Striae. 



Found in the middle and upper Rochester shale at Niagara. 



Strophonella ( ?) patenta Hall (Fig. 88). Leptaena pat- 

 en ta Hall (1852. Pal. N. Y. 2:60, pi. 21) 



Distinguishing characters. Wider than high; hinge not auriculate; 



Fig. 88 Strophonella (?, patenta with enlarged surface features 



fine unequal radii crossed by finer concentric striae; inner surfaces 

 of valves thickly covered with sharp points. 



Found in the Clinton limestones and lenses and doubtfully in the 

 middle Rochester shales at Niagara. 



Genus plectambonites Pander 

 [Ety.: -Xszrog, plaited; ap.fi <ov, beak] 

 (1830. Beitrage sur Gcognosie des Russ. Rciches. p. 90. Hall 

 & Clarke, 1892; Pal. N. Y. v. 8, pt 1, p. 236, 295) 



Shells small, concavo-convex; surface striae very fine, often alter- 

 nating in size; hinge line making greatest width, extremities often 



