SECTIOISr IV. 



LAMELLIBEANCHIATA FEOM THE MIDDLE MAEL BEDS. 



OSTREID^. 



Genus GEYPH^A Lam. 



Gryphaea vesicularis Lam. 



Plate XXVI, Fgs. 9 and 10. 



{For reference and synonymy see ante^ page 36.) 



The form of this species, which occurs principally in the Middle Marl 

 Beds, is that which is described on page 37, under the varietal name of G, 

 aucella Roemer, or at least very similar. The Xew Jersey examples do 

 not often have so straight a hinge-line as Dr. Roemer figures. For other 

 remarks see description of G. vesicularis. as above referred to. 



Gryphaea Bryani, var. precedens, n. var. 

 Plate XXVI, Figs. 7 and 8. 



This shell resembles Oystrea (Gryphcea) Bryani Gabb in many of its 

 features, but difi'ers very generally in being prolonged laterally on the left 

 side of the shell as one looks on the smaller valve. Considering this fact, the 

 shells may be said to be obliquely ovate in general outline, but with the left 

 side extended laterally in the lower half The lower valve is deeply concave, 

 and the beak usually shows a moderately large cicatrix of attachment. The 

 upper valve is concave and similarly extended as the lower. The muscular 

 imprint is of moderate size and irregularly circular, situated back of the 

 middle of the length, usually, and near the side. Cartilage area fairly 

 developed. Lateral margins of the valves strongly crenulated in the upper 

 third of the length and deeply sunken on the larger valve. This variety is 



194 



