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. Hérnes refers one of his Vienna 
shells to ventricosa, placing the Crag species with it as a synonym (Hornes, ‘ Foss. 
Moll.,’ vol. ui, p. 48). 
Panpora INEQuIVALVIS, Zinn. Crag Moll, vol. u, p. 270, Tab. XXV, fig. 5. 
Localities. Cor. Crag, Sutton, and near Orford. Red Crag, Walton Naze, and 
Waldrinefield. Middle Glacial, Hopton. 
I expressed my opinion in the ‘Crag Mollusca’ that emeguivalvis 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.2 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 znequivalvis as the Coralline 
Crag form and penna (obtusa) as the Red. Since then, however, I have found both in 
the Cor. Crag of Sutton, and Mr. Bell (‘ Ann. Mag.,’ May, 1871) gives odtwsa 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, Lanne. Crag Moll., vol. ui, 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- 
ington. 
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 Bridlmgton, 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 inthe Red. In the Fluvio-marine Crag, in the Chillesford bed, 
and in the Lower Glacial sands it is rare, but it is extremely common (though always 
