LAMELLIBRANCHIATA 



OF THE 



UPPEK IIELDERBEKG, HAMILTON, PORTAGE AND CflEMUNG GROUPS. 



II. 



DESCRIPTIONS OF SPECIP:S. 



MODIOMORPHA, Hall. 1870. 

 MoDioMORPHA Schoharie. 



PLATE XXXIV, FIG. 13 ; and PLATE XXXV, FIG. 14. 

 Mudiomorpha f^hoharle, H.\ll. PaL N. Y., voL v, pt. 1. Plates and Explanations: PL 34, fig-. 13. 18S3. 



Shell large, general form ovate, narrow in front; length one-third greater 

 than the height ; ventral margin broadly curved ; posterior margin abruptly 

 rounded. Anterior end obliquely truncate above, abruptly rounded below. 



Hinge-line oblique, equal to two-thirds the height of the shell. 



Beaks oblique, situated on the anterior fourth of the shell, depressed, rising 

 very slightly above the hinge. Umbonal region depressed convex. 



Test marked by strong, irregular, lamellose striae of growth, which are 

 stronger on the anterior end and pallia! margins. 



The muscular impressions are well-defined in the cast of the interior. 

 The anterior adductor is the smaller and situated in the lower portion of the 

 anterior end of the valve. The posterior adductor is sub-circular and located 

 in the lower portion of the post-umbonal slope. Pallial line deeply impres- 

 sed, following near to the ventral margin of the valve. 

 35 



