110 CYPRINID A. 
more limited degree, as the Cardiacee, of fixing itself firmly 
in the sand, generally choosing to have the umbones covered 
by it, and the orifices of the tubes of the mantle perpendicular. 
Resting in this position on the margin of a sand-bank, of 
which the surrounding soil is mud, at too great a depth to be 
disturbed by storms, the Jsocardia of our Irish Sea patiently 
collects its food from the surrounding element, assisted in its 
choice by the current it is capable of creating by the alternate 
opening and closing of the valves.” 
I have been tempted to copy the Rev. James Bulwer’s 
account of this animal from the second volume of the ‘ Zoolo- 
gical Magazine,’ rather than refer to it, as it smgularly corro- 
borates my views of the mode im which the branchie of 
bivalves are supplied with water. That gentleman, after many 
days’ examination, expressly states that the ingress current of 
water was effected by the opening of the valves, and which was 
expelled by their closure at the branchial orifice. This state- 
ment negatives the doctrine of branchial currents by cilia, 
and ingress and egress currents by separate apertures, that is, 
by the water being received by the branchial siphon or orifice 
and discharged from the anal one; besides, this result is 
anatomically impossible, as all my experiments—at least in the 
closed-mantle bivalves with elongated siphons— appear to 
prove that there is no communication between the anal and 
branchial tubes. In this species, the mantle being open, the 
branchize receive the water from the great ventral range, and 
it is expelled by the same channel. 
We are of opinion that the branchial cilia, the motive agent 
of the water with many authors, have no other function than 
to divide it, to facilitate the extraction of the vital influence. 
We strongly recommend those naturalists who advocate the 
doctrine of branchial currents by cilia and distinct siphons or 
apertures, carefully to consider Mr. Bulwer’s account, who at 
any rate must be looked on as a disinterested observer, and 
has no object in supporting a particular theory. 
This genus is artificial, and origmates in the shape of the 
shell; the animal is so similar to that of Cyprina, that Iso- 
cardia might very well merge in it. 
