MARYLAND GEOLOGICAL SURVEY 713 



Collections. Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences, New Jersey Geological Survey. 



Outside Distribution. Nagotliy Formation. Cliffwood clay, New 

 Jersey. Matawan Formation. Merchantville clay marl, Woodbury clay, 

 New Jersey. Black Creek Formation. Snow Hill, North Carolina. 



CORBULA CRASSIPLICA Gabb 

 Plate XLIII, Figs. 6, 7 



Corbula crassiplica Gabb, I860, Jour. Acad. Nat. Sci., Phila., 2d ser., vol. 



iv, p. 394, pi. Iviii, fig. 25. 

 Corbula crassiplicata Meek, 1864, Check List Inv. Fossils, N. A., Cret. and 



Jur., p. 15. 



Corbula crassiplicata Conrad, 1868, Cook's Geol. of New Jersey, p. 727. 

 Corbula perbrevis Conrad, 1875, Kerr's Geol. of North Carolina, App., p. 11, 



pi. ii, fig. 5. 

 Corbula crassiplica Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 178, 



pi. xxiii, fig. 30. 



Corbula crassiplica Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 17. 

 Corbula crassiplica Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, 



p. 641, pi. Ixxii, figs. 27, 28. 



Description. " Subtriangular, heavily ribbed, thick ; beaks large and 

 incurved ; umbones large and round ; umbonal ridge small and marked 

 by a distinct groove immediately in advance of it, rest of the shell marked 

 by about a dozen very coarse transverse ribs except on the umbones which 

 are smooth apparently from attrition. Inside hinge large, caudal pro- 

 longation marked by two pit-like depressions. Length .15 in., width .2 in., 

 height of right valve .07 in." Gabb, 1860. 



Type Locality. " From a cut on the Memphis and Charleston E. K., 

 where it crosses the Tennessee and Mississippi State Line." 



Shell small, high, trigonal, slightly inequilateral, very conspicuously 

 inequivalve ; right valve almost as high as it is wide, strongly inflated in 

 the umbonal region, the apices incurved, acute, prosogyrate and placed a 

 little in front of the median vertical; left valve oblong trigonal in out- 

 line, the altitude usually less than three-fourths of the latitude, the shell 

 evenly inflated and the umbones rather low and subcentral; anterior 

 dorsal and lateral margins of both valves evenly rounded, posterior dorsal 



