266 



Fig. 187. Tellbiopsis sub-emarginata. Two valves, showing variation in size and 

 form cfrom Hall). 



Found in the Strophalosia bed, in Avery's Creek, and the 

 shale just above it (very rare). 



Genus PHOLADELLA. Hall. 



[Ety. : Diminutive of the modern genus Pholas.] 

 (1870: Preliminary Notice Lamellibnincliiatu, 2, p. 68.) 



Shells with e<|ual iuecjuilateral valves, elongated, varying 

 in outline. Anterior end rounded or obliquely truncate; 

 posterior end truncate. Incurved anterior beaks; straight 

 cardinal line; prominent rounded or sub-angular umbonal 

 slopes; a deep, sharply -defined lunule; a well-marked 

 escutcheon; concentric stri<r and undulations, and distinct 

 radii, covering all but the anterior and cardinal slopes, — 

 mark this genus. 



Pholadella radiata. (Conrad.) (Fig. 188.) (Pal. 

 N. Y., Vol. v., Pt. I., p. 469, Pis. LXXVIIL, XCVI.) 



Distinguishing Cliaracters. — Small size; cuneate outline; 

 regularly rounded basal margin ; obliquely to vertically 



Fig. 188. Pholadella radiata. Two right and two left valves (from Hall). 



truncate posterior end ; anterior end obliquely truncate 

 above, by the deep lunule; cincture extending from beak to 

 base; fine concentric stria^, and strong radii. 



Found ten feet below the Encrinal limestone, at Section 7 ; 

 in the Modiomorpha sub-alata bed, in Idlew^ood Ravine, and 

 on the Lake Shore. 



