﻿128 



SUPPLEMENT TO THE CRAG MOLLUSCA. 



small piece has broken out of the hinge. It is from the Middle Glacial sand of Hopton, 

 and, like most of the specimens in that sand, is worn. 



« 



Lucina borealis. Crag Moll., vol. ii, p. 139, Tab. XII, fig. 1 ; Supplement, Tab. IX, 

 fig. 5. 



Localities. Cor. Crag passim. Red Crag passim. Fluvio-marine Crag passim. 

 Chillesford Bed, Chillesford, Bramerton, Aldeby, Easton, and Horstead. Lower Glacial, 

 Wey bourne (Reeve). Middle Glacial, Hopton and Billockby. 



This species is exceedingly common in the Cor. and Red Crags, as also in the Middle 

 Glacial Sands at Hopton, but in this latter it is generally in a fragmentary condition, 

 the only perfect valves that have occurred from these sands being those of very young 

 shells. 



The shell figured in this ' Supplement ' (Tab. IX, fig. 5) is of a specimen sent to me 

 by Messrs. Crowfoot and Dowson, who found it at Aldeby. In form it strongly 

 resembles L. spinifera, but I believe it is merely a distorted specimen of L. borealis. 



Diplodonta dilatata, S. Wood. Crag Moll, vol. ii, p. 145, Tab. XII, fig. 5. 

 Localities. As in 1 Crag Mollusca.' 



This was so called from a presumption that it was specifically distinct from rotundata, 

 which I still believe it to be. I also, in the ' Crag Mollusca,' placed B. dilatata, Sow., 

 from the older tertiaries of Sussex, as a synonym ; and gave as another synonym the 

 shell figured by Nyst under the name of B. dilatata, Phil. The shell figured by 

 Philippi under this name was, however, referred by him in a subsequent volume to 

 D. rotundata (' Phil.,' vol. ii, p. 24) ; while the shell figured by Nyst, and referred by 

 him to Philippi's so-called dilatata, is now called by Nyst B. Woodii, apparently under 

 the impression that Philippi's dilatata is a subsisting species, instead of its being 

 the same as B. rotundata. Nyst's figure ( £ Coq. Eoss. de Belg.,' pi. 7, fig. 1) 

 corresponds with the Crag shell, but his description, " son cote posterieur est tres elarge et 

 subanguleux," does not. My shell is also, I now believe, distinct from B. dilatata, 

 Sow., of Dixon's ' Geology of Sussex.' The nearest approach to it that I know is a shell 

 from Grignon (B. profunda, Desh.), but that is also, I believe, distinct. Under these 

 circumstances I have retained the Crag shell under the original name given by me to it in 

 1840, although it is placed by the author of the ' Brit. Conch.' as a variety only of rotundata. 

 B. dilatata is given by the late Dr. S. P. Woodward in his list of Norwich Crag shells, but 

 there is no authority attached to this name (unfortunately there are but few authorities for 

 names in that list), and I am not certain whether the species he speaks of be the 

 rotundata of Mont., or dilatata, S. Wood. 



