34 SECOND SUPPLEMENT TO THE CRAG MOLLUSCA. 



and, after the growth of two whorls, to change its form so as to produce a shell quite 

 unlike the oblate form of Natica, and of a more cylindrical shape. Our present shell is 

 much more tapering than Candida, and it possesses also one more whorl than the Red 

 Crag specimens of that species, though it has only half their linear dimensions. It 

 therefore seems to be a full-grown shell. 



Adeorbis ? NATicoiDES, S. Wood. 2nd Sup., Tab. Ill, fig. 13 a, <5. 



Diameter, xoth of an inch. 



Locality. Cor. Crag, Sutton. 



A small shell has been in my hands for many years, found by myself in the Cor. Crag 

 of Sutton. This has always much perplexed me, and it remained in my cabinet unfigured 

 and undescribed from the idea that it might be the young or embryo condition of some 

 larger species, and in the hope that I might obtain something further to assist in its 

 correct determination. Not having succeeded in this, I now figure the specimen as above. 

 I have a large number of very small specimens of several species of Natica, and have 

 broken up many of them with the expectation that I might produce something that would 

 show a keel round the umbilicus similar to the one in my present specimen, but without 

 success. There is a large umbilicus in some species of Natica, but in none can I find any 

 ridge around this great opening such as the shell now figured presents. Two very 

 anomalous shells, having large umbilical openings surrounded by a keel, have been figured 

 by the late M. Deshayes, viz. Lacuna onirabilis. 'An. du Bas. de Par.,' vol. ii, p. 372, 

 PI. XVIII, figs. 1 — 4, and Sigaretus problematicus, vol. iii, p. 90, PI. LXIV, figs. 7 — 9; 

 but neither of these correspond to our present specimen. There is also the living British 

 species. Lacuna pallidula, which possesses a somewhat similar keel round an open umbilicus; 

 but our shell has a distinct ridge or keel within the umbilical aperture, of which no species 

 of Lacuna that I have examined shows any trace. 



Delpldnula trigonostoma, ' Bast. Bord. foss.,' p. 28, PI. IV, fig. 10 (which I had given 

 as a synonym to Adeorbis subcarinata, but I believe erroneously), is perhaps the nearest 

 approach to my shell. I feel that the reference of the shell is very doubtful, but I give 

 it to draw the attention of collectors. 



Tkochus ziziPHiNTJS, Linn. 2ud Sup., Tab. IV, fig. 20; Crag Moll., vol. i, p. 124, 



Tab. XIII, fig 9 ; 1st Sup., p. 81. 



Dimensions. Height, -pg-th inch. 



Breadth, y^th inch. 

 Locality. Cor. Crag, Sutton. 



