1 82 NEW YORK STATE MUSEUM 



Genus strophonella Hall 



[Ety. : (jrf)6(po<s^ turned around] 



(1879. ^^- ^- ^^^'tc mils. nat. hist., 26th an. reft, p. 153; Hall & 

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



Shells with the form and structure of Strop heodonta, 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, fig. 7) 



^#a,«i»' te^,^, Distingviishing characters. Semielliptic, almost 



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 auric.ulate; 



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.: vrAsxro?, plaited; aixfiov, beak] 



(1830. Beitrdge zur Geognosie des Russ. Reiches. p. 90. Hall 

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



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

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



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