76 MOLLUSCA FROM THE CRAG. 



Shell turriculate, with flat volutions, subcarinate at the base; finely striated 

 transversely, and banded at rather irregular distances, with two or three obtuse 

 ridges, the upper one nearly obsolete. 



Axis, 1\ inches. 



Locality. Cor. Crag, Gedgrave and Ramsholt. 



Red Crag, passim. Recent, Mediterranean. 



This species is abundant, and very variable in regard to the number and 

 arrangement of its banded ridges. That which I considered as a distinct species, 

 and named bicinctus (Tab. ix, fig. 7 d) when my Catalogue was published, I have 

 now reason to believe is only a variety. The young or upper volutions of most 

 specimens have the banded ridges more prominent and distinct than upon the 

 larger part of the shell. Fig. 7 a appears to correspond with Brocchi's figures 

 (Tab. vi, figs. 12 and 13), which are, I imagine, only varieties with more elevated 

 ridges. 



Figs. 7 a, d, are from the Coralline Crag. 



Figs. 7 b, c, are from the Red Crag. 



4. TURRITELLA PLANISPIRA. S. Wood. Tab. IX, fig. 11. 



Turritella planispira. S. Wood. Catalogue 1842. 



Nyst. Coq. foss. de Belg. p. -101, pi. 38, fig. 9, 1844. 



T. Testa turritd, subulatd ; anfractibus planalis ; transversim striatis ; striis reyu- 

 laribus sub-aquidistantibus. 



Shell turreted and tapering, with nearly flat volutions ; transversely striated ; 

 strice regular, nearly equidistant. 



Axis, 1| inch. 



Locality. Cor. Crag, Sutton. 



I have only been able to procure fragments of this species, and they appear to 

 agree with the shell figured by M. Nyst. The whorls are very flat, with scarcely 

 a distinct suture in some specimens. In the young state the middle ridge is 

 always the most prominent, taking off from the flatness of the volution, which 

 distinguishes it when further increased. The ridges or striae are generally regular, 

 though sometimes alternating, one large and one small. M. Nyst, as well as 

 myself, have considered this distinct, and it is rather singular that we should both 

 have chosen the same name for it. It is, however, possible this may be only a 

 variety of T. communis, but I have never seen that shell with such perfectly flat 

 volutions, or so subulate in form. 



5. Turritella clathratula. S. Wood, 1847. Tab. IX, fig. 6, 8 a. 



T. Testa turritd, subulatd; anfractibus novem convcxiusculis ; lineis quinque elevatis 

 transversis cinctis ; interstitiis striatis vel clathratis ; aperturd subquadratd. 



Shell turreted and tapering, with about nine slightly convex volutions, orna- 

 mented with five transverse rather rounded ridges ; the sulci between them longi- 

 tudinally striated or imbricated ; aperture subquadrate. 



