546 Systematic Paleoxtology 



division between the upper and lower portions of the valve. The margin 

 of the upper division is obliquely truncate, receding from below to the 

 hinge line, and strongly curved inward at the central emargination. 

 Lower section also strongly lobed and somewhat rounded. 



" All the specimens seen are quite imperfect, and are more or less casts 

 of the interior. The strong line of division between the upper and lower 

 sections of the valve gives one the impression of a double shell, or of two 

 distinct shells united along the margins ; and were it not for the surface 

 markings they would greatly resemble in form that of a large Conularia." 

 —Whitfield, 1885. 



The species is represented in the area under discussion by only the most 

 fragmentary material, in the shape of rudely conical, longitudinally sili- 

 cate casts, some of which were at first mistaken for fragments of teeth. 



Occurrence. — Matawan Formation. Post 105, Chesapeake and Dela- 

 ware Canal, Delaware. 



Collections. — Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences, New Jersey Geological Survey, TJ. S. National Museum. 



Outside Distribution. — Matawan Formation. Merchantville clay marl 

 and Woodbury clay, New Jersey. Monmouth Formation. Navesink marl, 

 New Jersey. Ripley Formation. Exogyra costata zone, Pontotoc and 

 Union counties, Mississippi. 



Family PERN11DAE 



Genus INOCERAMUS Parkinson 



[Trans. Geol. Soc, London, 1819, vol. v. p. 59] 



Type. — Inoceramus cuvieri Sowerby. 



Shell fragile, of two component layers, the inner layer thin and nacreous, 

 the outer much heavier and prismatic in texture; inequilateral and fre- 

 quently inequivalved, varying in outline from subcircular to trigonal, 

 oblong or cordate, produced transversely, obliquely or vertically; valves 

 compressed or inflated, often unequally so; lunule and escutcheon not 

 defined, as a rule ; umbones usually more or less anterior and prosogyrate, 



Etymology: U(lv-), fibre; /cepa/ios, earthen-ware; probably from a fancied 

 resemblance of the fibrous outer layer to broken pottery. 



