Contributioris to Invertebrate Palaeontology. 559 



Genus GRAMIWYSIA DeVerii. 



Graiuniysia Ibisiilcata. 



Plate XI, fig. 19. 



P/ioIaJomija anomala Goldf. Pet. CTermanica, p. 272, pi. 157, fig. 9. 

 Pleriueu Inmlcata Conrad, Ann. Rept. Geol. Surv. N. Y., 1838, p. 1(5. 

 Cypricardites bisulcaia Conrad, Ann. Kept. Geol. Surv. N. Y., 1841, p. .^2. 

 Grammi/sia Hamiltonensis DeVern., Bui. Geol. Soc, France, 2d Series, vol. 4, 



p. 69G, 1S47. 

 Cardinia Hamiltonensis DeOrb., Prod. Pal?eon., vol. 1, p. 7(:), 18.'iO. 

 Grammysia bisidcata Conrad, H. and W. Prelim. Notice Lamellib. Shells of the 



Up. Held. Hamilton and Chemung Groups. Published as ext. from 



Pvept. State Cab., Dec. ISGi). (Anonymously.) 



Specimens of this species, presenting all the specific features of 

 the typical forms from the Hamilton beds of New York, and found 

 at Fishinger's Mills, Sciota, Ohio, in beds of limestone above the 

 " Bone-bed." 



The general form is transversely elliptical, a little more than 

 half as long again as high, the valves usually compressed some- 

 what in the direction of bedding, but still moderately convex and 

 extremely Unio-like in their general expression. The body of the 

 valves is marked by the characteristic oblique rib and furrow pass- 

 ing from the beak to the postero-basal margin, somewhat modify- 

 ing its border; also by numerous concentric folds or wrinkles 

 parallel to the margin of the shell, and marking stages of growth. 

 These wrinkles are usually well marked on the anterior end of the 

 shells, and become faintly marked or obsolete posterior to the ob- 

 lique furrow, and on the rather wide posterior cardinal slope. The 

 hinge-line is nearly straight and shorter than the length of the shell 

 behind the beaks, causing an oblique truncation of the posterior 

 end above the longest point of the valve. Beaks large, tumid, 

 situated well forward on the valves and enrolled. The oblique 

 ridge is generally more or less nodose from the crossing of the con- 

 centric folds of the shell. 



This species has always been considered a very characteristic and 

 well-marked Hamilton type ; and its occurrence in layers above the 

 horizon of the " Bone-bed," and not below, is very significant. 



