MARINE MOLLUSC A OF THE UNITED STATES. 13 



Shell at first discoidal, becoming decollated when adult ; tubular, cylindri- 

 cal, arched ; aperture round, entire ; apex closed by a mammillated 

 septum ; operculum horny, many-whorled. CAECUM, Fleming. 



Shell mostly pure white and lustrous ; turreted ; many-whorled ; whorls 

 round, sometimes separate, ornamented with numerous transverse ribs ; 

 aperture round ; peristome continuous ; operculum horny, few-whorled. 



SCALARIA, Lamarck. 



Genus TURRITELLA, Lamarck. 



Prodr. 74. 1801. 



The animal in this genus has long, subulate tentacles ; eyes 

 slightly prominent; foot truncated in front, rounded behind, 

 grooved beneath ; branchial plume very long ; lingual ribbon 

 minute, denticulated. Carnivorous ? 



The species range from low water mark to 100 fathoms ; their 

 geographical distribution is extensive, embracing most tropical 

 and temperate seas. 



1. T. EROSA, Couthouy. Fig. 130. 



Bost. Journ. Nat. Hist., ii. 103, t. 3, f. 1. 1838. 

 T. polaria, Moller, Ind. Moll. Scand. 1843. 



Shell turreted, elongated ; whorls nine to eleven, rather flat, 

 smooth, sloping towards the suture ; from three to five abruptly 

 revolving grooves, most prominent and numerous on the lower 

 whorls ; striae of growth wrinkling the shell longitudinally ; apex 

 often eroded; aperture circular; lip thin and impressed by the 

 termination of the costae ; coluinella with a slight callus and 

 angular base ; reddish-brown. 



Length 12.5, diam. 3.75 mill. 



Massachusetts, northwards (Eur.). 



2. T. RETICULATA, Mighels and Adams. Fig. 131. 



Bost. Journ. Nat. Hist., iv. 50, t. 4, f. 19. 1842. 

 T. lactea, Moller, Ind. Moll. Scand. 1842. 



Shell turreted, slender, grayish-white ; whorls eleven or twelve, 

 convex, with irregular longitudinal folds, and three to five re- 

 volving striae, making the surface appear reticulated; aperture 

 small, orbicular ; labrum thin ; operculum horny. 



Length It, diam. 5 mill. 



Allied to T. erosa, but easily recognized by the longitudinal 

 ribs, and by its more slender form. 



Gulf of St. Lawrence. 



