GASTEROPODA. 31 



it is by no means rare. The costae are about 11 in number on the last volution, 

 and stand apart ; they are not so wide as the spaces between them, and are crossed 

 by about ten sharp and elevated strise, which are carried over the ribs, and the 

 mouth has a thickened varix when full grown. This species appears subject to very 

 little variation ; among all my specimens there is but a trifling difference. It is 

 more distinctly costated and more elongated than the two preceding. The costae 

 in the figure given by M. Nyst are represented as close together. In the English 

 specimens there is a considerable space between them. The mouth is subcircular, 

 with about a dozen denticulations within the outer lip, and sometimes three or four 

 at the lower part of the columella. In one specimen the whole of the left lip is 

 covered with denticulations. 



6. Nassa consociata. S. Wood. Tab. Ill, fig. 7. 



Nassa costula. S. Wood. Catalogue 1842. 



N. Testa turritd, angustd, elegante ; spird elevatd, apice obtusiusculo, longitudinaliter 

 costatd, costis 9 — 10 rectis, transversim crenulatis ; aperturd orbiculari ; labio swpeme 

 uniplicato ; labro incrassato intus rare dcnticulato. 



Shell turreted, with an elevated spire, and rather obtuse apex, longitudinally 

 costated, costae 9 — 10 transversely crenulated ; aperture orbicular, with a tooth on 

 the left lip ; base rather contracted and reflected, outer lip dentated within. 



Axis, f of an inch. 



Locality. Cor. Crag, Sutton and Gedgrave. 

 Red Crag, Sutton. 



I possess only a few specimens of this shell from each formation, which I have 

 considered as distinct. It somewhat resembles N. elegans, but differs in several 

 characters. The transverse ridges are more obtuse than in N. elegans, and almost 

 invisible between the ribs, which are prominent and distant. The mouth has exter- 

 nally a thickened varix in the adult state, and the lip is much thickened within, 

 with four or five obtuse dentations. The siphonal canal is deeply indented and 

 reflected towards the back. It differs from the figure of B. pusillum, Phil. (t. 27, 

 f. 15), in having the volutions more convex, and the costse more distinct, with a 

 more circular aperture, and fewer dentations, and it may be considered intermediate 

 between that species and N. elegans. It is more elongated and elegant than B. 

 graniferum, Dujardin, and has the costae further apart. 



7. Nassa monensis. Forbes. Tab. Ill, fig. 5. 



Nassa monensis. Forbes. Proceedings of Geol. Soc. vol. iv. 

 — proxima. S. Wood. Catalogue 1842. 



N. Testa elongato-ovatd, turritd, longitudinaliter costatd ; anfractibus convcxis, striatis ; 

 suturis prqfundis ; costis 12 ; aperturd ova id ; labio unidentato ; labro intus denticulato. 



Shell elongato-ovate, turreted, longitudinally costated ; whorls convex, rugosely 

 striated ; suture deep ; costae 10 — 12 ; aperture ovate, with a tooth at the upper 

 part of the left lip ; outer lip dentated within. 



