MYA. 167 
even the excuse of an extraordinary number of species as a 
sort of palliation for its constitution. 
M. oBionea, nobis. 
Lutraria oblonga, Chemnitz. 
5 Brits;Molk 1. p;3/4, spl. 13.,fa1- 
Mactra hians, Mont. et Auct. 
Animal oblong, tolerably thick, very pale yellow, with the 
mantle closed, except a large anterior fissure for the foot; it 
is also produced into a large, rugose when contracted, sheath, 
but not so much so as in M. truncata. The ground colour is 
white, but covered with a brown epidermis, which also is 
deposited on the ventral regions of the mantle; the common 
sheath, containing the two siphons, can be greatly inflated, 
and is often extended twice the length of the shell; it only 
just bifureates at the terminus, showing the orifices of the 
siphons ; the anal is of much less calibre than the branchial, 
and encircled by 30-40 short, fine, simple, red-brown cirrhi; 
the branchial has about the same number, of similar colour, 
half of which are stronger and longer than the others, bemg 
fimbriated on each side; the remainder are interstitial. The 
foot is large, rather fleshy and lingwiform, white, with a tinge 
of pale brown, and without a byssal groove. On each side 
there are a pair of branchize and palpi; the former are narrow, 
not strictly linear; the upper one is not so deep as the under 
one anteally, but posteally they are much of the same dimen- 
sions, having their points deposited in the branchial siphon ; 
they are pale drab, with the transverse vessels of the circulation 
well marked on both sides. The palpi are very large, triangular, 
pointed, of very thin membranous texture, pale brown, and 
elegantly aspersed with minute red-brown pomts; the two 
pairs are united by plain labia passing around the mouth. 
We have taken this species at Exmouth alive: though very 
large valves are taken in the dredge, and continually cast on 
shore, it is smgularly scarce, probably inhabiting the littoral 
limits, and lodged so deep as to escape detection and the action 
of the dredge. The above is taken from a fine 4-imch spe- 
cimen sent me to Bath, this 21st January, 1851, having been 
