56 



CORBULID.^. 



CoRBULA GIBBA"*, Olivi. 



Tellina gibba, Olivi, Zool. Adr. p. 101. C. nucleus, F. & H. i. p. 180, pi. ix. 

 f. 7-12, and (animal) pi. G. f. 3. 



Body whitish, with often a tinge of yellow : mantle thick ; 

 its edges minutely ciliated : tubes contiguous, very short, and 

 scarcely protruded beyond the valves, edged with narrow lines 

 of pink or orange a little below the extremities ; orifices fringed 

 with conical and rather slender cirri or tentacles (from 8 to 12 

 round each), having truncated points ; these cirri are trans- 

 parent, and spotted with a few flake- white marks, and each is 

 encircled at its base by a line of red dots ; hyaline apparatus 

 of the upper tube bell-shaped, retractile, and in frequent 

 action : gills very unequal, hanging obliquely, the upper one 

 narrow, and the lower one larger and more triangular ; they 

 are brown, smooth outside and finely striated within : palps 

 long, narrow, pointed, pendulous, and brown, pectinated 

 strongly on both surfaces : foot large and thick, very fleshy, 

 bent near its junction with the rest of the body, sometimes 

 forming an elongated cone and byssiferous : liver dark green. 



Shell triangularly oval ; right valve much larger and more 

 gibbous than the left, which it overlaps to a considerable ex- 

 tent ; left valve compressed towards the front and sides ; the 

 substance is thick and opaque, and the surface of the right or 

 deeper valve is more glossy than that of the other, and occa- 

 sionally iridescent : sculpture, numerous concentric stria?, which 

 in the smaller valve are slight and irregular, and are often 

 crossed by a few raised lines radiating from the beaks, but in 

 the larger valve these stria? usually become cord-like and close- 

 set ribs : colour white, with more or less of a yellowish or 

 reddish-brown tinge, sometimes varied by longitudinal rays or 

 streaks of the latter hue on the larger valve : epidermis brown, 

 thick, and somewhat fibrous, mostly abraded and wanting on 

 the larger valve : margins rounded on the anterior side and in 

 front, truncated on the posterior side (which is depressed and 

 diagonally separated in the smaller valve, and twisted in the 

 other valve), with a slight groove or fold proceeding from below 

 the beak ; dorsal margins straight : beaks calyciform, obliquely 

 incurved to the anterior side ; umbones prominent and conti- 

 guous ; dorsal excavation generally deep, but not distinctly 

 defined : cartilage small, narrow, and triangular, composed of 

 several leaflets, which represent the successive accretions of 



* Gibbous. 



