﻿BIVALVIA. 



105 



A single specimen, as above represented, is all that I have obtained or seen from the 

 Upper Tertiaries of East Anglia which could be referred to this species. The artist has 

 not made the figure sufficiently elliptical, and it possesses thirty-eight fine, delicate, closely 

 set ribs. Since the engraving was made, however, I have obtained some intermediate 

 forms, which induce me to doubt whether the present specimen, as well as that 

 figured from the Coralline Crag as varius, may not be merely extreme modifications of 

 P. opercularis. 



Pecten pusio, Pennant. Crag Moll., vol. ii, p. 33, Tab. VI, fig. 4. 



Localities. Cor. Crag passim. Red Crag, Walton and Sutton. Middle Glacial, 

 Hopton. Upper Glacial, Bridlington? 



Some fragments of this species have occurred in the Middle Glacial sand, but they are 

 rare. Its occurrence in the Fluvio-marine Crag seems doubtful, and I have not met with 

 it from the Red Crag of Butley. There is a specimen in the British Museum presented by 

 Dr. Murray with the locality of Bridlington attached to it, but it seems so unlike in colour 

 and condition to the Bridlington fossils that its occurrence at that locality seems doubtful. 

 Although very abundant in the Cor. Crag, I have never seen a specimen that showed 

 marks of attachment by the exterior of the valve. 



Pecten opercularis, Linn} Crag Moll., vol. ii, p. 35, Tab. VI, fig. 2 ; and Supplement, 



Tab. VIII, fig. 6. 



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

 Whitlingham, Thorpe, and Bulchamp. Chillesford bed, Aldeby and Chillesford. Middle 

 Glacial, Billockby and Hopton. 



The figure in Supplement represents a small shell from the Cor. Crag, which I think 

 belongs to this species ; it is about half an inch in diameter. It appears to be a distor- 

 tion, and resembles the figure of Ostrea arcuata, Broc. (' Conch, foss. Subapen./ tab. 

 xiv, fig. 2), which is probably a distortion. This species is common in some of the 

 localities of the Fluvio-marine Crag, and rare at others. It occurs, though not commonly, 

 in some of the localities of the Chillesford bed, but I have not met with it from either 

 Horstead, Burgh, or Coltishall, or with any trace of it in the Lower Glacial sands. In a 

 fragmentary state it is very abundant in the Middle Glacial sands at Billockby, Clippesby, 

 and Hopton. 



1 In the 'Ency. Method.,' pi. 314, fig. 1 b, is the figure of a shell with its animal inhabitant. This 

 figure which seems very fanciful, was probably intended for P. opercularis, but the animal is represented 

 as havinga large protruding foot on one side with two projecting siphons on the other. 



