28 MOLLUSCA FROM THE CRAG. 



aperture ; outer lip generally thickened and dentated within, with a short and some- 

 what reflected canal ; operculum corneous. 



This genus is not admitted by all conchologists as a necessary separation from 

 the Linnsean genus Buccinum, and in fact Lamarck subsequently reunited them 

 without assigning any reason for so doing. The principal distinctive character 

 given, is the prominent tooth at the base of the columella, and, it might also be 

 added, the denticulations within the outer margin of the aperture, and the expanded 

 form of the inner lip. There certainly is a close resemblance between some species 

 of each, but such is the case with all approximate genera in their aberrant forms. 

 Two or three species have been figured from the Green-sand as belonging to this 

 genus, and a few doubtful shells are given from the Eocene formations. The Crag 

 deposit is exceedingly rich, not only in individual specimens, but also in number of 

 species. The range of this genus in depth seldom exceeds sixteen fathoms, while 

 some of the species are found under stones at low water. 



1. Nassa labiosa. /. Sow. Tab. Ill, fig. 8, and Tab. VII, fig. 22. 

 Buccinum labiosum. J. Sow. Min. Con. t. 477, 1824. 



— Nyst. Coq. foss. de Beige, p. 577, pi. 43, fig. 14, 1844. 



Nassa labiosa. S. Wood. Catalogue 1842. 



N. Testa ovatd ; spird elevatd ; transversim proj "unde sulcata ; apice dcuminato ; anf fac- 

 tious septem convex iusculis ; suturis profundis, canaliculatis ; labio extenso ; labro intus 

 denticulato ; canali brevi. 



Shell ovate, with an elevated and acuminated spire, ridged or sulcated along the 

 volutions, with a small canal at the suture ; inner lip thick and extended on the 

 body whorl ; outer lip denticulated within ; canal short. 



Axis, f of an inch. 



Locality. Cor. Crag. Gedgrave. 



Red Crag, Sutton and Newbourn. 



Not very abundant. When perfect the spiral ridges are generally regular, flat, as 

 broad as, and sometimes broader than, the spaces between them. The inner lip is much 

 spread and smooth, and the upper angle of the mouth slightly elevated, producing 

 thereby a small but distinct canal at the suture ; canal short, slightly recurved, with 

 about a dozen denticulations within the outer lip. It has a fold or ridge at the base of the 

 columella, with two or three wrinkles on the lower part of the left lip. This is given 

 by Professor E. Forbes, in his ' Report upon the Geological Relations of the existing 

 Fauna and Flora of the British Isles,' as a synonym to B. semistriatum, Broc. If it be 

 the same species, it is very differently ornamented upon the exterior. The Crag shell 

 ismore elongated than any of my specimens of B. semistriatum, and it isregularly striated 

 or ridged all over, and rather more strongly so upon the body of the shell. In B. semi- 

 striatum it is strongly and coarsely striated only at the base, nor are there any longitudi- 

 nal folds upon the upper volutions ; lines of growth are faintly visible over the shell. 



In Table in, fig. 8, the artist has given too great an expansion to the lower 

 portion of the outer lip. Table vn, fig. 22, is a more correct representation. 



