TELLINA. 129 
animal is like that of T. tenuis, which has only a single amal- 
gamated branchial lamina on each side, and belongs to our 
second section; in that case, the 7. fabula must march with 
it. But this poimt may easily be set at rest, as the species is 
common, though not in my district. The 7. proxima is exotic 
or fossil. The 7. bimaculata is exotic. 
The 7. balaustina of British origm has much similarity to 
specimens of 7. crassa of the same size; the hinge, teeth, cica- 
trices, and pink radiating pencils are identical ; the chief dif- 
ference is the greater tumidity and tenuity of the valves, and 
the absence of the short vertical lines between the striz of 
increment. 
Section II. Animal with a single branchia on each side. 
T. tenuis, Da Costa. 
T. tenuis, Brit. Moll. i. p. 300, pl. 19, f.8; and (animal) pl. K. f. 3. 
Animal very flat; mantle sufficiently open in the ventral 
range, finely fringed, produced posteriorly into two white 
siphons, separated from their bases, of about equal length and 
diameter ; both of them are often exserted beyond the length 
of the shell; the anal is usually the longest, and curves up- 
wards; but these circumstances depend on the will of the 
animal. There is only one very large pale brown, excessively 
membranous, subtriangular branchia, on each side, with the 
finest pectinations, fixed under the posterior dorsal range, 
where its point becomes united with that of the one on the 
other side, exactly as in 7. solidula, but its margin is not 
fixed to the body so decidedly; it is more lax, and can be 
elevated by a camel’s-hair brush, and is connected at the 
anterior angle by a branchial vein, with a pair on each side of 
large triangular palpi, but not so much out of size as im 
T. solidula and Scrobicularia piperata; they are pectinated on 
both sides, but more so on the inner surfaces; the colour is 
a darkish cloud hue, mixed with paler lines, giving them a 
mottled aspect ; they are broad at the bases, not very long or 
pointed. The foot is large, broad, compressed, tongue-shaped, 
not very pointed, and geniculated. The liver is dark green ; 
K 
