MARYLAND GEOLOGICAL SURVEY 595 



Collections. Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences, New Jersey Geological Survey. 



Outside Distribution. Matawan Formation. Merchantville clay marl 

 and \\ y oodbury clay, New Jersey. Monmouth Formation. Navesink marl 

 (rare), New Jersey. 



PECTEX SIMPLICIUS Conrad 

 Plate XXXIV, Figs. 8, 9 



Pecten simplicius Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2d ser, vol. iv, 



p. 283, pi. xlvi, fig. 44. 

 Sincyclonema f simplicus Meek, 1864, Check List Inv. Fossils, N. A., Cret. 



and Jur., p. 7. 



Pecten simplicus Conrad, 1868, Cook's Geol. of New Jersey, p. 725. 

 Sincyclonema simplicus Gabb, 1876, Proc. Acad. Nat. Sci., Phila., p. 319. 

 Amusium simplicum Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 51, 



pi. vii, figs. 11, 12. 

 Pecten simplicius Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, 



p. 480, pi. li, fig. 6. 



Description. " Ovate, thin, smooth and shining; ears moderate, nearly 

 equal ; both valves slightly convex ; the upper valve slightly tumid on the 

 umbo ; inner margin minutely crenulated." Conrad, 1860. 



Type Locality. Eufaula, Alabama, or Tippah County, Mississippi. 



Shell small, smooth, lustrous, moderately compressed, the left valve a 

 little more so than the right ; anterior and posterior lateral margins con- 

 verging at an angle of from 70 to 90, base broadly and evenly arcuate; 

 hinge-line straight, a little less than half the latitude of the shell, auricles 

 small, trigonal, the anterior slightly larger than the posterior and sinuated 

 in the right valve to accommodate the bvssus ; sinuses between the auricles 



O i/ 



and the disk clearly defined; external surface highly polished, smooth 

 excepting for faint incremental striations and an occasional microscopi- 

 cally fine radial shagreening ; characters of the interior unknown. 



This Pecten, in spite of its small dimensions, is a conspicuous factor in 

 the Cretaceous marls of Maryland by reason of its wide distribution and 

 its shining surface. This shell is so thin and flaky, however, that for all 

 it is so common it has not been possible to separate any one of the forms 

 from its matrix. 



