32 EOCENE MOLLUSCA. 



" The Woolwich type of this species is generally smooth ; but I have reason to think that 

 the fibrous striated coat is more easily decomposed than the other laminae of the shell, and 

 has been therefore generally destroyed. Such appears to have been the case often with the 

 Bracklesham individuals ; however, some of the latter, having the fibrous coat, are almost 

 free from stria?, and others want them over more or less of the surface, which has induced 

 me to consider the striated ones as only varieties of the others." (Sowerby in Dixon.) 



In support of the above remark, I may observe, that some of Mr. Edwards' specimens 

 from Bracklesham show the upper valve to be quite free from ornament ; others are 

 fully covered over with numerous fine stria? ; and one specimen unites these two varieties, 

 the younger half of the upper valve being covered with stria?, and the lower or older por- 

 tion being quite plain ; both parts are apparently without decortication. 



0. angustata, Desh., in many characters strongly resembles this species; but it appears 

 rather more attenuated in the hinge than any of our British specimens, although such a 

 difference as this may be accidental. In the representation of the Erench shell are a few 

 depressed and irregular ribs, and the shell is free from stria?, but there are vestiges of 

 radiating plica? or obsolete ribs in our species. 



The full-grown specimens may be said to have proportions generally of about three to 

 one, but a full-grown specimen in Mr. Edwards' cabinet is not more than two to one and a 

 half. In the young state the shell is often nearly orbicular, becoming elevated as it increases 

 in size. One of our specimens has a very pointed umbo, and this is somewhat recurved. 



21. Ostrea Vectjensis, Forbes MSS. Tab. VII, fig. 5, a — c. 



Ostrea Vectensis. Morris. Mem. Geol. Surv. pp. 68, 150, t. 3, lig. 9, 9 a, 9 b, 185G. 

 — — Id. Cat. Brit. Foss., p. 175, 1854. 



Spec. Char. "Testa ovato-trigond, oblongd, attenuate!, sub-angustd ; area cardinali 

 fossuld triangulari, lata, recurvd exaratd ; umbonibus obtusis ; valvd supcriore lineis incre- 

 ment numerosis ornatd ; valvd majore crassd, cxtiis rugosd." 



An oblong and rather narrow shell, with the larger valve somewhat thick and externally 

 rugose ; the upper valve flat, thin, recurved at the umbo, and marked by numerous con- 

 centric lines of growth ; ligamental area broad and triangular." (Morris.) 



Longest diameter, 1^ inch. 



Locality. " Sandy beds of the Bembridge series." {Morris.) 



This species does not appear to be rare ; several specimens are in the Museum in 

 .lermyn-street. 



The right valve has occasionally crenulations in the margin near the hinge ; but 

 as this valve is often quite free from them ; the form of the shell is also exceedingly 



