



TURBJNACEA. MOLLUSCA. LACUNA. 263 



nating in an umbilicus ; as the two margins join each other at the 

 base, they form a slight projecting angle. A slight angular ridge 

 revolves from the upper angle of the aperture, on some specimens 

 quite perceptible. Operculum horny, sub-spiral. Length j inch, 

 breadth T 3 T inch, divergence 589. 



Variety FUSCA. Figure 169. Shell proportionally shorter, 

 more solid and opake, of a darker, generally uniform color, some- 

 times yellowish, and sometimes purplish horn-color, occasionally 

 with one or two bands, or banded shades ; the mouth more angu- 

 lar, and the angular revolving ridge more frequently conspicuous. 



Found, driven up, on all our beaches, and alive among the roots 

 of Laminaria and other marine plants, attached to stones and 

 shells, and dragged by storms from deep water* 



It is easily distinguished from all our shells by its peculiar umbili- 

 cus, and its elongated form, by which it is distinguished from the next 

 species. The size above given is larger than in most specimens, but 

 not so large as in many. It is undoubtedly the L. vincta of the British 

 shores, as settled by actual comparison and the opinion of Mr. Sower- 

 by. Mr. Conrad seems not to have been acquainted with the L. vine- 

 ta, when he described his L. pertusa, distinguishing it from L. quad- 

 rifasciata. The variety is found in about equal numbers with the 

 type. It does not depend on age; for small young specimens are 

 proportionally short, dark, and solid. But the approaches to each other 

 are so insensible, that I do not venture to make a species of it ; but 

 attach to it, as a variety, a name some years since proposed for it 

 by A. Binney, a Representative. It may prove to be a technical spe- 

 cies, and perhaps is actually the Turbo canalis, Mont. 



LACUNA NERITOIDEA. 



Shell globular-ovate, with three whorls and a half, the last 

 very large, smooth, yellowish-green ; aperture semi-lunar, oblique ; 

 umbilicus large and deep. 



FIGURE 170. 

 State Coll., No. 35. Soc. Cab., 2413. 



Lacuna neritoidea, GOULD ; SilUmaris Journ., xxxviii. 197. 



