606 Systematic Paleoxtology — Upper Devonian 



MOLLUSCA 



Class PELECYPODA 



Order PRIONODESMACEA 



Family GRAMMYSIIDAE 



Genus GRAMMYSIA de Verneuil 



Grammysia elliptica Hall 

 Plate LIX, Figs. 1], 12 



Grammysia elliptica Hall, 1870, Notice Lammelllbranchiata, vol. ii. p. 53. 

 Gravimysia elliptica Hall, 1885, Pal. of N. Y., vol. v, pts. i, ii, p. 365, pi. Iviii, 

 figs. 1-12. 



Description. — Shell transversely elliptical, basal margin broadly curv- 

 ing, slightly sinuate about the middle ; posterior margin abruptly rounded 

 below and curving into the cardinal line above, sometimes more or less 

 truncate. Valves regularly convex becoming more or less gibbous in the 

 imibonal region. Beaks subanterior, prominent, incurved; cincture ex- 

 tending obliquely to the base of the shell. Surface with fine irregular 

 concentric striae which become aggregated into fascicles at the front and 

 middle of the shell. 



Length 50 mm.; height 40 mm. 



In New York it has a notable vertical range from the beds with the 

 Ithaca fauna upward into the higher Chemung strata. 



Occurrence. — Jennings Formation, Chemung Member. One mile 

 east of Barrelville near top of Chemung; Allegany Grove, 1633, 2800; 

 Town Creek, 3870, 3963, 3969. Parkhead Member. Town Creek, 

 1605; 2 miles west of Pawpaw, West Virginia, 1484. 



Collection. — Maryland Geological Survey. 



Grammysia subarcuata Hall 

 Plate LIX, Fig. 13 



Grammysia subarcuata Hall, 1870, Prel. Notice Lammellebr., vol. ii, p. 61. 

 Grammysia subarcuata Hall, 1885, pal. of N. Y., vol. v, pt. i, ii, p. 375, pi. 

 Ixi, figs. 10-22, pi. xciii, fig. 26. 



