﻿BIVALVIA. 



157 



which specimen, in its turn, did not quite correspond with Phillips' description of this 

 species. 



I have not been able to clear up this doubt, but Dr. Homes refers one of his Vienna 

 shells to ventricosa, placing the Crag species with it as a synonym (Homes, ' Foss. 

 Moll.,' vol. ii, p. 48). 



Pandora inequivalvis, Linn. Crag Moll, vol. ii, p. 270, Tab. XXV, fig. 5. 



Localities. Cor. Crag, Sutton, and near Orford. Red Crag, Walton Naze, and 

 Waldringfield. Middle Glacial, Hopton. 



I expressed my opinion in the ' Crag Mollusca ' that inequivalvis and pinna were not 

 entitled to specific separation, following in this Montague, and I only separated them out 

 of deference to the authors of the ' British Mollusca.' As my view has received the 

 support of the author of the ' Brit. Conchology,' it seems desirable to unite the two forms 

 under the same specific name. In the ' Crag Moll.' I gave inequivalvis as the Coralline 

 Crag form and pinna {pbtusa) as the Red. Since then, however, I have found both in 

 the Cor. Crag of Sutton, and Mr. Bell ('Ann. Mag.,' May, 1871) gives obtusa from the 

 Cor. Crag near Orford. 



The hinge portion of one specimen has occurred in the Middle Glacial, but to which 

 of the two varieties it belongs cannot be said. 



Saxicava arctica, Linne. Crag Moll., vol. ii, p. 287, Tab. XXIX, fig. 4, and p. 285, 



Tab. XXIX, fig. 3, as S. rugosa. 



Localities. Cor. Crag, Sutton. Red Crag, Walton, Sutton, and Butley. Fluvio- 

 marine Crag, Bramerton. Chillesford bed, Bramerton and Aldeby. Lower Glacial, 

 Belaugh. Middle Glacial, Billockby and Hopton. Upper Glacial, Bridlington and Dim- 

 lington. 



I observed in the ' Crag Mollusca ' that, although I had kept arctica and rugosa as 

 distinct species, I did not believe in any grounds for their distinction. I have, therefore, 

 now united them. The very gigantic rugosa form, so characteristic of the Canadian beds, 

 seems confined to the later glacial beds of Britain, as it appears only at Bridlington, Dim- 

 lington, and in the yet more recent Clyde deposits. It belongs to the truly arctic fauna that 

 established itself in Britain towards the close of the glacial period, and seems absent from 

 the older glacial beds, in which the small smooth form alone occurs. The rugose form 

 occurs in the Coralline and Red Crags, but of smaller size. The species is common in 

 the Cor. Crag, but not so in the Red. In the Pluvio-marine Crag, in the Chillesford bed, 

 and in the Lower Glacial sands it is rare, but it is extremely common (though always 



