16 EOCENE MOLLUSCA. 
about ten years, but to come to perfection in four or five. Fishermen pretend to be 
able to tell the age of this Mollusc by the discoloured fimbriations upon the lower valve, 
somewhat like the hybernating marks upon the snail. 
1. Osrrea apuata, S. Wood. Tab. V, fig. 3, a—c. 
Spee. Char. O. testa minimd, ovato-elongatd vel irregulariter cuneatd, apice obliquo ; 
valud inferiore radiato-costatd, plus minusve profundd ; valvd superiore planiusculd vel con- 
veatusculd ; marginibus superné granoso-plicatis ; impressione musculari sublunart. 
Shell small, ovately oblong, or irregularly wedge-shaped, apex oblique; lower valve 
radiately costated, more or less deep; upper valve flat or convex, margin near the hinge 
crenately plicated; muscular impression sublunate. 
Longest diameter, 1 inch nearly. 
Locality. Oempstead, Isle of Wight (Zdwards). 
There is something peculiar about this little shell which seems to entitle it to an isolated 
position, and J have, in consequence, given it anew name. It is a miniature representation 
of O. flabellula, but the coste are fewer and do not appear to be visible in the young 
shell. All the specimens I have seen are attached to Cerithium plicatum ; this, perhaps 
being the most abundant univalve in the deposit, has been selected for that purpose, and 
the oyster has sometimes fixed itself in the direction of the height of the univalve, by which 
it has become elongated from the umbo to the ventral margin, and has thereby altered 
the natural form of the shell. In one or two specimens the costa are obsolete or scarcely 
visible, and the margins of the valves near the hinge appear to have interlocked ; 
having crenulations in the right valve corresponding with depressions in the left for 
their reception. ‘The cylindrical support of the animal has not only reduced the depth or 
capacity of the lower valve, but this internal prominence has communicated its form to the 
upper valve, making it very convex. It is similar in habit to O. mutadilis, Desh. Coq. 
Foss. des Env. de, p. 344, pl. 56, f. 9-10, but that species does not appear ever to 
have had its lower valve plicated. 
2. OstREA aLiena, S. Wood. ‘Tab. VIII, fig. 2. 
Spec. Char. O. testé tenui, ovatd vel ovato-rotundatd, valvd inferiore convexiusculd, 
extus irregulariter costulato-radiatd, sub-lobatd. 
Shell thin, ovate or ovately rounded ; inferior valve slightly convex, and covered with 
radiating ribs or riblets, and slightly lobed. 
Diameter, 3 inches. 
Locality. Bracklesham (#dwards). 
There are a few specimens of Ostrea in Mr. Edwards’s cabinet, which I cannot 
satisfactorily assign to any species known to me, and I have given to them the above 
name provisionally. 
