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 

 Linnaean 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 denticu- 

 lations 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 seldoms 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. 



Bdccinum labiosum. J. Sow. Min. Con. t. 4/7, 1824. 



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



Nassa labiosa. S. Wood. Catalogue 1842. 



N. Testa ovafd ; spird elevatd ; transversim profunde sulcatd ; apice acmninato ; 

 anfractibus septem convexiusculis ; suturis profimdis, canalicidatis ; lahio extenso ; lahro 

 intiis 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, 2 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, \\-ith 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 difl"erently ornamented upon the exterior. The Crag shell 

 is more elongated than any of my specimens of B. semis^-iatum, and it is regularly 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 longitudinal 

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



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

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



