260 



Found nine to twelve feet below the Encrinal limestone, at 

 Section 7 (very rare). 



Genus GRAMMYSIA. DeVeeneuil. 



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

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



Shell ^vith 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 nmrked by concentric strict and 

 frequently b}^ concentric undulations. Ligament external, 



Grammysia ARCUATA. (Courad. ) (Fig. 179.) (Pal. N.Y.. 

 Vol. v., Pt. I., p. 373. Pis. LXI., LXIII.^XCllI.) 



Distinguishing Chnraaters. — Sub-anterior l>eaks ; uniformly 

 rounded anterior and posterior ends ; strong, uniform con- 

 centric undulations, which pass around the shell from lunule 



Fig. l?d. (.Trammysia arcuata. Left and right valves (from Hallj. 



to escutcheon; fine, close, concentric striiie; cincture a mere 

 flattenhig. 



Found nine to twelve feet below the Encrinal limestone, 

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

 questioimble). 



Note. — Although the genus Grammysia is well rep- 

 resented in the Hamilton group in central and eastern New 

 York, it appears to be almost unrepresented in this portion 

 of the State. 



