MOLLUSCA. 481 



slightly rounded on me outer margin and forming a slight byssal 

 notch at its junction with the body o<f the shell on the right 

 valve. Cardinal slopes on the right valve straight to near the 

 point of greatest width of the valve, and forming an angle of 

 about fifty to fifty-five degrees with each other and very strongly 

 impressed. Beak small and pointed. On the left valve the 

 posterior ear is the smallest of the two, and the cardinal slopes 

 less strongly marked, not so straight, and extend down the 

 valve not so far as on the opposite valve. Surface of the valves 

 smooth and shining to the naked eye, but under a lens is seen 

 to be marked by fine concentric lines of growth, and on the left 

 valve by faint, incipient, radiating lines." (Whitfield.) 



Remarks. Whitfield' s description quoted above, is drawn 

 from Alabama specimens of this species, all the New Jersey 

 material at his disposal being "too 1 imperfect for illustration." 

 The species is also- extremely rare in the more recent collections 

 of the Survey, nearly all the shells of this type being marked 

 with conspicuous concentric lines, which have been made the 

 chief characteristics of the species Pecten conradi Whitf. A few 

 individuals of a small Pecten from the Tinton beds, however, 

 the largest of which does not exceed 10 mm. in height, seem to 

 be characterized in the impressions of the external surface, by 

 their perfectly smooth shells, and have been identified with Con- 

 rad's species. 



Formation and locality. Red Bank sand, near Middletown 

 (112), Tinton beds, Tinton Falls (no), Beers Hill cut (i29 5 ), 

 near Freehold ( 1 32 ) . 



Geographic distribution. New Jersey, Alabama, Mississippi, 

 Arkansas, Texas. 



Genus NITHE;A Drouet. 



Neithea quinquecostata (Sowerby). 



Plate LI., Figs. 7-12. 

 1814. Pecten quinquecostata Sow., Min. Conch., vol. I, p. 122, 



pi. 56, figs. 4-8. 



1830. Pecten quinquecostatus Morton, Am. Jour. Sci., ist ser., 

 vol. 17, p. 285, vol. 18, pi. 3, fig. 5. 

 31 PAI, 



