168 MYAD A. 
cast on shore at Exmouth during the late gales; it arrived 
quite lively, wrapped in fucus, and accompanied by sea-water. 
It proved an important acquisition. I ascertamed, both 
anatomically and practically, that there is no connection 
between the branchial and anal ‘siphons, affording another 
proof that there is an end to the doctrine of separate branchial 
currents by cilia. 
M. evuiprica, nobis. 
Lutraria elliptica, Lamarck. 
, Brit. Moll. i. p. 370, pl. 12; (animal) pl. H. f. 2. 
Mactra lutraria, Auctorum. 
Animal compressed, subovally elongated, white. The mantle, 
ventrally, has the margins united by a fine, white, minutely 
crenulated line, which marks the suture, except for a space 
of about one-third of the posterior portion of the pedal fissure, 
which is edged by rather distant fine white filaments, and 
affords a passage for a large thick tongue-shaped white foot, 
without a byssal groove. The siphonal sheath is very large, 
subcylindrically tapering, and, in a shell of 35 inches trans- 
verse measure, is, when in full activity, 6 inches long ; from its 
base for 2 inches it is white, and for another 2 inches marked 
with zigzag purplish-brown blotches, which at the terminal 
portion become distinct, dark purplish-brown dots; on the 
surface of the sheath there are two or three circular brown 
lines, an inch apart, and it is covered with a transparent 
corrugated skin, which appears to be a prolongation of the 
light horny epidermis that clothes the exterior of the entire 
area of the valves; within the sheath are the anal and 
branchial siphons, both furnished at their terminations with 
numerous white cirrhi, minutely spotted with dark purplish- 
brown or red; the branchial cilia are the longest, delicately 
fimbriated on the margins with alternate smaller and shorter 
ones; the anal are of the same colour, but shorter and more 
numerous. The branchize are pale brown lamin, not deep, 
the upper ones being rather the lesser; they are hung trans- 
versely, with their points lymg in the branchial cavity; the 
minute vessels of the circulation give them the appearance of 
