280 



NOBTH-CAKOLINA GEOLOGICAL SURVEY. 



S(hell comparatively thin, and light and compressed valves; 

 circular, sometimes oblique and equilateral ; ribs twenty-four, 

 marked on the outside with concentric squamose lines of 

 growth, which are undulating, the last of which are strong ; 

 lower valve less convex than the upper. It differs from the 

 comparilis in being concentrically marked, and thinner, be- 

 sides it grows much larger. 



PECTEN PKINCEPOIDES. N. S. (Fig. 198.) 



Shell large, rather thick, compresed, sub-inequilateral, ra- 

 diating striae coarse and very numerous ; transversely marked 



by lines of growth, giving the surface a wrinkled appear- 

 ance; ears unequal ; buccal ear sinuate, radiating striae nu- 

 merous, inside smooth, striae obsolete ; tig. reduced. 



This is a large species of pecten, is closely allied to the P. 

 princeps of the English crag. It is common in the miocene 

 marl on the Meherrin river, at Murfreesboro'. It is five 

 inches long, and five and a quarter wide. It is readily dis- 

 tinguished by the absence of ribs proper, and the presence 

 of coarse radiating striae, which have intermediate ones, 



