GASTEROPODA. 79 



This was found by Mr. Bell, to whom I am indebted for the use of the specimen for 

 the above figure ; it is the only one I have seen from the Crag. 



Littorina rudis, Maton. Supplement, Tab. V, figs. 9 and 10 a, b. 



In my Monograph, vol. i, p. 118, Tab. X, fig. 14, a — /c, I have given figures and 

 descriptions of a variety of forms of shells belonging to the genus Littorina, from the 

 Fluvio-marine Crag of Norfolk and Suffolk, which I had considered as all belonging to 

 one species, littorea, and I have here had figured two or three more to show the 

 extraordinary range in variation to which they had been subject. The British Con- 

 chologists, although they have kept separate several forms of this genus, have no 

 accordance respecting specific division. 



I have obtained a very large number of specimens of Littorina from the JFluvio- 

 marine Chillesford bed, at Horstead and Coltishall, and from the Lower Glacial sand at 

 Belaugh, and these correspond principally with the form usually seen in our markets. 

 With these, as might be supposed, are small or young specimens strongly marked with 

 spiral striae and with a well-defined suture, while the large or full-grown specimens are 

 nearly smooth. Two or three of the distorted figures of Littorina, ' Crag Mol./ vol. i, 

 Tab. X, fig. 14, may probably be referred to what is called rudis. Mr. Jeffreys says 

 (vol. iii, p. 367) that rudis is viviparous, and littorea oviparous. If this be so, that 

 distinction might entitle them to be considered as more than specifically distinct ; but 

 as far as their testaceous covering goes there seems so much intermingling of character 

 between rudis and littorea, not to speak of the numerous other forms treated as species 

 or varieties, that I confess to the greatest uncertainty in assigning shells to these 

 respective species separately ; what seems to be L. rudis from Bramerton is shown in 

 Tab. V, fig. 9 ; and a distortion of the same species from the same place, put into my hands 

 by Mr. Horace Woodward, is shown in fig. 1 0. L. littorea occurs also in the Middle 

 Glacial at Hopton and Billockby, in the Upper Glacial at Bridlington, and in the Post- 

 Glacial Gravels of March, Hunstanton, and Kelsea Hill, and in the Nar Brickearth. 



Lacuna reticulata, S. Wood. Crag Moll., vol. i, p. 122, Tab. XII, fig. 10. 



Macromphalus reticulatus, S 1 . Wood. (Catalogue of shells from the Crag.) Ann. 



Nat. Hist., 1842, p. 537. 



This shell is excessively rare to my researches, and I am unable to give to it any 

 additional particulars; it does not strictly conform to the characters of the genus as 

 generally described, but it has a broad and flattened pillar lip or elongated umbilicus ; 

 it nearly resembles Lacuna elegans, Deshayes, ' An. sans Vert, du Bas. de Par.,' vol. ii, 

 p. 371, PI. XVII, figs. 4 — 6, but it is probably distinct. Another species, somewhat re- 

 sembling it, is placed in the same genus by Dr. von Koenen, 'Mittel Olig. Norddeutschlands,' 



