S T R ^ A. 



Plate V. 



Species 8. (Fig. as, 6, c, d, e,f, Mus. Jeffreys.) 



OsTRiE.\ EDULis. Ost. tcstd ovato-suUrigotid, soUdd, 

 intils plerumque nived, ad latera jyrope cardinein 

 plm minusve deniiculatd, viargine ventrali sub- 

 rotundo et expanso ; margine dorsali subauricu- 

 lato ; valvd inferiori plerumque concavd, obtvse 

 radiatim costata, lamellis undulatim plicatis, laxe 

 hnbricatd, purpurea irregulariter strigatd ; valvd 

 superiori rrdiiori, plerumque valde complanatd 

 fusco - viridescenti, purpurea obscure radiatd, 

 squumis compresds, laxis, subquadratis, mullilo- 

 baiis, radiatim di!'2)osilis laniinatd. 



The edible Ostr^\. Shell ovately subti-igonal, solid, 

 generally snow-white within, near the hinge at the 

 sides more or less denticulated, ventral margin 

 rather rounded and expanded ; dorsal margin 

 subauriculated ; lower valve generally concave, 

 obtusely radiately ribbed, loosely imbricated with 

 wavily plicated lamellae, irregularly striped with 

 purple ; upper valve smaller, mostly very flat, 

 greenish brown, obscurely rayed with purple, 

 laminated with flattened, loose, many-lobcd, 

 radiately-disposed scales. 



LiNN^us. Systema Naturte, No. 1148. 



Ostrcea parasitica, Turton. 



Ostroea hippopus, Lamarck. 



Hab. Europe. 



The common eatable European oyster may be consi- 

 dered as presenting a fair specimen of one characteristic 



of its tribe, namely, extreme variabihty of form. The 

 principal varieties are arranged as follows by Mr. 

 Jefifreys, premising that the tjqie is of a dull greenish- 

 brown and a little inclined to a trigonal form. 



Var. \. pardsitica (fig./), which adhering by a large 

 part of its undersurface to various shells and other 

 substances, modifies its form by them. In the beauti- 

 fully leafy and variegated specimen here figured may be 

 seen the traces of the ribs of Fccten opercularis to 

 which it is attached, showing through both valves. 



Var. 2. OsfrcB(zAip^qp»;s, Lamarck, is not gregarious, 

 like the ordinary forms, but solitary, and living in 

 deep water ; is very rough and ponderous, not at all 

 flaky or scaly ; very deep in the lower valve and 

 thick in the upper. 



Var. 3. defomiis, Lam. (a term which might apply 

 to irregularly growing shells of any of the species). 

 Two examples are given (/, r, d,) one elongated per- 

 pendicularly, and the other laterally, the latter being 

 formed upon the operculum of a living whelk and con- 

 fined in its growth to the shape of the aperture. 



Var. 4. nitupina, Jefir. A small, regiilarly formed, 

 not very flaky variety, to which our '• Natives" 

 belong. 



Var. 5. tinrfa, Jeffr. Like var. rutiipina, rather 

 regularly formed and flat, but having the inside coloured 

 with purplish brown. (Fig. o.) 



October, 1870. 



