200 



tliaii half the length of the shell, and barely arcuate. Anterior end somewhat 

 narrow and short ; beneath the beaks, which are close to the anterior end, is 

 a very small, but strongly marked, lunule ; the margin here is broadly rounded 

 into the basal border, which is regularly curved except where the oblique 

 fold or rib terminates. The posterior margin is sharply rounded, prolonged, 

 and slightly oblique to the transverse axis. Surface ornamented with concen- 

 tric striae and undulations of growth, parallel with the margin, which are 

 strongly marked on the anterior end and umbo, but disappear on the posterior 

 slope and cardinal region. There are traces also of an oblique middle fold or 

 rib, extending from the beak to the basal margin, considerably behind the 

 middle of the valve. This fold or rib is not deeply marked in the specimen 

 figured across the entire valve, but its termination on the margin shows plainly 

 a protrusion and the two adjacent depressions or /urrows. 



The species resembles Grammysia Elliptica, but the valves are very ven- 

 tricose, the umbo unlike Elliptica, and in other characteristics quite different. 



Formation and Location : Chemung Group, Belvidere, Allegany Co., N. Y. 



The great depth and position of the rocks in this group, extend- 

 ing as they do over the southern tier of counties of New York, 

 southward in Pennsylvania, and along the Appalachian region, 

 make them of more than ordinary interest. 



They consist mostly of shale and intervening sandstone, in 

 which the shale greatly predominates. 



In no part of the group is there a greater abundance of fossils or 

 variety of species to be found than between the Genesee and Alle- 

 ghany rivers, over an area some thirty miles in width from the 

 Pennsylvania line. The Genesee at Belvidere is about 1,700 feet 

 above tide water, while the hills which lie to the south and south- 

 west reach an altitude of 800 or 1,000 feet above the flood plain of 

 the river. The lower strata, as exposed in the deep ravines and 

 along the natural water-courses of streams tributaries to this river, 

 are found in many places to be wonderfully fossil iferous; nor is it 

 only at the base, but on the tops of the elevations, wherever the 

 shale or sandstone come to the surface, that both brachiopoda and 

 lamellibranchiata occur. 



At Belvidere, on Van Campen's creek, is a layer of grayish sand- 

 stone, about two feet thick, in which the Grammysia Chemungensis 

 was found; and so full is this rock of shells, that scarcely a square 

 iuch of it can be exposed without disclosing some specimen. 



