260 



Found nine to twelve feet below the Encrinal limestone, at 

 Section 7 (very rare). 



Genus GRAMMYSIA. DeVekneuil. 



[Ety. : Gramme, a line of writing; mys, a mussel shell.] 

 (1847: Bull. Soc. Geo. France, 2d Ser., Tome IV., p. 696.) 



Shell with equal inequilateral valves, which are trans- 

 versely elliptical or sub-ovate. The beaks are prominent 

 and incurved, and in front of them is a strong, heart-shaped 

 depression, or "lunule," while behind them a similar, but 

 somewhat elongate, impression, or "escutcheon,'' occurs. 

 Usually an oblique cincture and fold traverse the shell from 

 beak to base. The surface is marked bv concentric striae and 

 frequently by concentric undulations. Ligament external. 



Grammysia arcuata. (Conrad.) (Fig. 179.) (Pal. X.Y.. 

 Vol. V.. Pt. 1.. p. 373, Pis. LXI., LXIII, XCT1I.) 



Distinguishing Characters. — Sub-anterior beaks ; uniformly 

 rounded anterior and posterior ends ; strong, uniform con- 

 centric undulations, which pass around the shell from lunule 



Fir;. 179. Grammysia arcuata. Left and right valves (from Hall). 



to escutcheon; fine, close, concentric stria?; cincture a mere 

 flattening. 



Found nine to twelve feet below the Encrinal limestone, 

 at Section 7 (a fragment, the identification of which is 

 questionable). 



Note . — Although the genus Grammysia is well rep- 

 resented in iln- Hamilton group in central and eastern New 

 York, it appears to be almost unrepresented in this portion 

 of the State. 



