venus. 339 



They differ considerably in the comparative convexity, 

 and in the ribs being more or less laminar or numerous. 

 I do not regard the V. refleoca of Montagu as a dis- 

 tinct variety ; for every possible gradation may be seen, 

 connecting it with the typical form. The dorsal margin 

 in this species and V. fasciata not ^infrequently assumes 

 a serrated appearance, arising from the extremities of the 

 ribs projecting on that side. V. Casina may be known 

 from the last-mentioned species by being much larger 

 and broader, the ribs more laminar, delicate, and flounce- 

 like, the longitudinal striae proportionally stronger, the 

 umbones usually not so prominent, and the colour more 

 sober and less diversified. 



The present species is the Pectunculus membranaceus 

 of Da Costa, V. erycina of Pennant (but not of Linne), 

 and V. lactea of Donovan ; in its younger state it appears 

 to be the V. cancellata of Donovan, V. discina of La- 

 marck, V. Rustericii of Payraudeau, and V. casinula of 

 Deshayes. 



6. V. verrucosa*, Linne. 



V. verrucosa, Linn. Syst. Nat. p. 1130; F. & H. i. p. 401, pi. xxiv. f. 3. 



Body very thick, pale yellowish-white : mantle freely open 

 from the tubes to the anterior adductor muscles ; its edges are 

 serrated or fringed, presenting more or less of a furbelowed 

 aspect : tubes short, but well separated, and of a yellowish- 

 white colour, with tawny specks or dark-grey spots, lines, and 

 small blotches ; the orifice of the branchial tube is surrounded 

 by a double series of cirri, the largest of which (about twenty 

 in number) are simple ; there are only about ten simple and 

 shorter filaments around the orifice of the smaller and upper 

 tube, which is furnished with a prominent conical valve : gills 

 nearly circular, free, of a brown colour, coarsely pectinated ; 

 the upper pair is, as usual, smaller than the under: palps 

 rather small and narrow : foot white, moderately long, tongue- 

 shaped and pointed, when at rest axe-shaped ; it exhibits no 

 trace of a byssal groove. 



* Warty. 



q2 



