GASTEROPODA. 31 



by no means rare. The costse are about 1 1 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 striae, 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 costge 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 GOSTULA. S. Wood. Catalogue 1842. 



N. Testa turritd, angustd, elegante ; spird elevatd, apice obtusimculo, longitudmaliter 

 costatd, costis 9 10 reef is, transversim cremdatis ; aperturd orbiculari ; labio superne 

 uniplicalo ; labro incrassato intus rare denticulato. 



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

 costated, costa3 9 1 transversely crenulated ; aperture orbicular, with a tooth on the 

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



Axis, 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. elegam, 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 externally 

 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 distant, 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 convexis, striatis ; 

 suturisprofundis; costis 12; aperturd ovatd ; labio unidentato ; labro intus denticulato. 



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

 striated ; suture deep ; costse 10 12 ; aperture ovate, with a tooth at the upper part 

 of the left lip ; outer lip dentated within. 



