ISO AMERICAN MARINE CONCIIOLOGY. 



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Genus PECTUNCULUS, Lam. 

 Syst. 115. 1801. 



Animal with a large crescent-shaped foot, margins of the sole 

 undulated ; mantle ojjen ; margins simple, with minute ocelli ; gills 

 equal, lips continuous with the gills. 



About sixty species known, ranging from 8 to over 100 fathoms. 



1. P. PENNACEUS, Lamarck. Fig. 473. 



Aiiim. sans Vert. 

 P. lineatus, Reeve Zool. Proc. 1843. 

 P. spadiceus^ Reeve, Zool. Proc. 1843. 



Shell orbicular, swollen, decussately striated, longitudinal strine 

 the strongest; whitisli, irregularl}'^ painted with large and small 

 dark-brown spots and streaks ; umbones bent inwards to the an- 

 terior end of the ligament. 



N. CarMna to West Indies. 



This shell has been doubtfull}- referred by some conciiologists 

 to P. Gharlestoniensis.1 a post-pliocene fossil of S. Carolina. 



Genus NUCTJLA, Lamarck. 

 Syst. 115. 1801. 



Animal with the mantle open, its margins plain; foot large, 

 deeply fissured in front, forming when expanded a disk with ser- 

 rated margins; mouth and lips minute, palpi very large, rounded, 

 strongly plaited inside, and furnished witli a long convoluted ap- 

 pendage; gills small, plume-like, united behind the foot to the 

 branchial septum. 



Distribution about 70 species, from 5 to 100 fathoms. 



1. N. TENUIS, Montagu. Fig. 478. 



Test. Brit. Suppl. 56, t. 29, f. 1. 1808. 



Shell small, thin, trapezoidal ; smooth, without radiating lines ; 



beaks prominent ; epidermis grass-green ; inner margin entire. 



Length 7.5, height 6.25 mill. 



Maine, nortlncards. {Ear.) 



2. N. PROXiMA, Say. Figs. 479, 480. 



Journ. Philad. Acad., ii. 270. 1822. 

 Area nucleus, Linn (part). Syst. Nat., edit. xii. 1143. 



Shell oblique, ovate-triangular, crossed bj^ minute concentric 

 and radiating lines; epidermis olivaceous; margin crenulated; 

 hinge-teeth large, twelve before and eighteen behind the beaks. 

 Length 11, height 9 mill. 



Whole Coast, soutlncards to N. Car. (Eur.) 



