New Upper Silurian Fossils. 121 



IX. — Descriptions of New Species of Fossils, from the Upper 

 Silurian Boclcs of Port Jervis, N. Y.; with Notes on the 

 occurrence of the Coralline Limestone at that Locality. 



By S. T. BARRETT. 

 Read January 28, 1878. 



Genus DISOIIA, Lamarck. 



DISCINA JERVENSIS, New Species. 



Shell obtusely oval in outline, extremities equal and broad- 

 ly rounded; dorsal valve depressed convex; apex midway 

 between the centre and the posterior margin, abruptly ele- 

 vated behind and sloping gently forward, the lateral slopes 

 ending in a broadly flattened margin ; ventral valve slightly 

 elevated in front of the foramen, and broadly concave between 

 this elevation and the anterior margin. Foramen oval, about 

 the same distance from the posterior border as the apex of 

 the upper valve. The impression of the outer surface of the 

 lower valve shows the imprint of fine raised concentric striae, 

 about seven of them to one-twelfth of an inch of the longer 

 diameter near the front of the shell. The upper valve is 

 similarly striated, and its cast has the apex divided by an 

 impressed line, which is prolonged toward the front. Length 

 of an average specimen, ten lines; greatest breadth, eight 

 lines. Elevation of apex, 0.15 of an inch. The upper and 

 lower valves of this shell are often found united, but with 

 their surfaces so much injured by exfoliation that the ex- 

 ternal markings are only determinable by an examination of 

 the matrices, which are generally covered with a thin portion 

 of the shell. 



This fossil is very abundant in a layer situated among the 

 higher strata of the Oriskany group, at Port Jervis, N. Y., to 

 which village.the specific name refers. 



