GASTEROPODA. 35 



it is particularly large. In some specimens the striae are very conspicuous, while in 

 others they are somewhat indistinct ; they may, however, be traced in every specimen. 

 The left Up extends some way over the body of the shell, and there is a prominent 

 ridge on the edge of the columella, as pointed out by Mr. J. Sowerby in ' Min. Conch.,' 

 corresponding in these characters with the genus Nassa, but it has a large and open 

 aperture, with a plain and simple outer lip, which is free from denticulations. It may 

 be considered as a rather aberrant form connecting the two genera. 



Buc. ovum, Turt., has hitherto been represented and described as a perfectly smooth 

 shell, and considered, in consequence, as a new species, distinct from B. Balei, with 

 which it agrees in all its other characters. Professor E. Forbes, however, has informed 

 me that Mr. M'Andrew has detected some faint traces of strise upon a specimen of 

 B. ovum in his possession. It may then, I think, be fairly presumed as identical with 

 B. Balei of the Red Crag, and its extreme rarity be looked upon as the dying out of 

 a species once exceedingly abundant in this country ; and in thus becoming extinct, 

 may not its want of, or rather its famt and imperfect strise be from failure in vigour 

 in those organs necessary for such distinction, consequent upon the approaching demise 

 of the species ? 



2. BucciNUM UNDATUM. Linii. Tab. Ill, fig. 12, a — d. 

 BucciNDM UNDATUM. Linn. Syst. Nat. p. 1204, 1766. 



— STRIATUM (?). Penn. Brit. Zool. iv, p. 121, 1776. 



— UNDATUM. Brown. Illust. Brit. Conch, pi. 49, fig. 8, 1827. 



— Anglicanum (?). - - - pi. 49, fig. 11. 



— TENERUM. J. Sow. Min. Concli. t. 486, fig. 3, 1825. 



_ _ Nijst. Coq. foss. de Belg. p. 571, pi. 43, fig. 9, 1844. 



— UNDATUM. S. Wood. Catalogue 1842. 

 Tritonium UNDATUM. Loven. Ind. Moll. Scand. p. 12, 1846. 



Bale. Hist, and Antiq. of Harwich, pi. 10, fig. 8, 1730. 



B. Testa ovato-conicd, ventricosd, striata, costatd, undulatd; anfradibus convexis ; 

 aperturd ovatd, labro sinuato, canali brevissimo aperto. 



Shell ovato-conical, ventricose, generally thin, with, sometimes wdthout, undulate 

 costse ; whorls convex ; aperture ovate, with a thickened and slightly sinuated outer 

 lip ; base emarginate ; canal short and open. 



Axis, 3 inches. 



Locality. Cor. Crag, Ramsholt. 



^ Red Crag, Butley, Newbourn, Sutton, and Walton. 



Mam. Crag, Bridlington. Recent, British and North Seas. 



This shell first appears in the Coralhne Crag, where, however, it is by no means 

 abundant. In the Red Crag it becomes more so ; but the greater number of the 

 specimens, being much reduced in substance, are fragile, and difiicult to obtain ; the 

 outer coating having been in some instances entirely removed, its peculiarly striated 

 markings are thereby obliterated. Some specimens so precisely resemble the common 



