Mabyland Geological Survey 545 



The genus belongs to a very ancient group, prominent in the Paleozoic 

 faunas. Pinna itself is not certainly known from strata older than the 

 Jurassic. It was moderately abundant, however, during the middle and 

 late Mesozoic, but less so, apparently, during the Tertiaries and the 

 Quaternary. The genus is quite well represented in the warm waters of 

 the recent seas, the byssus of some of the recent species being remarkable 

 for its length and silky texture. That of Pinna nobilis Lam., of the 

 Mediterranean, is used by the Sicilians for the manufacture of the so-called 

 " cloth of gold," an exceedingly soft and pliable silken fabric. 



Pinna laqueata Conrad 

 Plate XXI, Fig. 12 



Pinna laqueata Conrad, 1858, Jour. Acad. Nat. Sci., Phila., 2d ser, vol. iii, 



p. 328. 

 Pinna laqueata Meek, 1864, Check List Inv. Fossils, N. A., Cret. and Jur., 



p. 9. 

 Pinna laqueata Conrad, 1868, Cook's Geol. of New Jersey, p. 725. 

 Pinna laqueata Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 81, pi. 



xvi, figs. 1, 2. 

 Pinna laqueata Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 10. 

 Pinna laqueata Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, p. 419, 



pi. xxxvi, fig. 1. 



Description. — " A fragment — ventricose, with eleven prominent, 

 slender ribs ; interstices concave." — Conrad, 1858. 



Type Locality. — Owl Creek, Tippah County, Mississippi. 



" Shell of moderate size, very rapidly expanding from the apex and 

 ventricose, giving a subquadrangular section. Surface marked by from 

 nine to eleven strong, simple, radiating ribs on the dorsal portion, which 

 are broad and rounded on the top and separated by very broad concave 

 interspaces. The lower or basal portion is marked by very strong con- 

 centric stria? parallel to the margin, so very irregular as to often form 

 strong undulations of the surface. Line of division between the tipper 

 and lower sections of the valves very strongly marked on the cast, often 

 presenting the appearance of a distinct suture. Posterior margin of the 

 shell apparently double, being deeply emarginate or lobed at the line of 



