NASSA. 363 



elevated spire, rather l)lnnt at the apex, which, however, is gen- 

 erally much eroded ; suture distinctly marked ; surface marked with 

 numerous unequal, revolving lines, which are crossed by 

 minute lines of growth, and larger or smaller, more or less ^'^' ^^^' 

 numerous oblique folds ; these always exist on the smaller 

 whorls, but are often entirely wanting on the lower whorl, 

 the whole giving the shell a granular appearance ; aper- 

 ture oval, outer lip simple and sharp, not thickened with- 

 in, but marked with elevated lines not reaching the mar- „ ;, , . 



■ ~ N. obsoleta. 



gin, in adult specimens ; pillar deeply arched, overspread 

 with enamel, having a protuberance or fold at its front, turning into 

 the interior ; canal a mere notch ; throat purplish-black, fading 

 within, and, in almost every instance, with a bluish-white band at 

 its posterior third ; something similar is found on the opposite lip ; 

 operculum horny, not serrated. Length, one inch ; breadth, one 

 half inch ; divergence, fifty degrees. 



The animal is variously mottled with slate color ; the foot is as 

 long as the shell, its anterior angles prolonged and turned l^ack- 

 wards ; head not extending beyond the shell ; eyes black, on the ex- 

 terior side of the tentacula, and above the base ; above the eyes the 

 tentacula are suddenly diminished, and bristle-shaped ; trunk cylin- 

 drical, channelled beneath, half as long as the shell, and very con- 

 spicuous. 



Its movements are very active, and it collects in numbers about 

 dead cra])s and other marine animals, on which it feeds. 



Inhabits all our muddy shores, preferring situations not exposed 

 to the surf of the open sea ; such as inlets and extended flats which 

 are drained at low tide. It is found abundantly at the confluence 

 of fresh and salt water, whore the taste is merely brackish. Profes- 

 sor Adams remarks, that the finest specimens he had found " were 

 growing at Nantucket, where they are as abundant as in any of our 

 continental harbors." 



No shell of equal size is so abundant on the whole Atlantic shore. 

 Specimens from Florida vary only in l^eing smaller, more oliva- 

 ceous, and by having a thick, broad callus over the pillar. 



The younger shells are most likely to be collected, because the 

 old ones become very much eroded and defaced, and a greenish, 

 mould-like plant vegetates abundantly upon them. Very few, there- 

 fore, of the shells usually collected have the lines on the interior 

 of the outer lip. Kieuer's figure represents an immature shell. 



