146 ANATINID ZS. 
The ground colour of the animal is hyaline white; the mantle 
is considerably extended beyond the margins of the shell, and 
is of azure hyaline, edged with brillant silvery, close-set, sym- 
metrical, blunt, short, but distinct dentations, which extend 
on both sides to near the beaks ; consequently it 1s open from 
the anterior side, throughout the ventral range, to the sessile 
anal tube, which is scarcely visible, bemg within the margins 
of the shell, from which we saw ejected the elongated oval 
drab pellets: this is the only apparent siphonal orifice. The 
foot is very large, long, broad, subtriangular, hyalme, well 
suffused with flake-white points ; it is usually protruded m the 
centre of the ventral range, and the animal frequently passes 
it from stem to stern; it is slightly geniculated and has a 
decided byssal groove. 
The animal is lively, marches with rapidity, and in its course 
turns from side to side, sometimes resting the shell on the 
ventral range in an upright posture. The branchiz and palpi, 
from their minuteness, escaped observation. It inhabits the 
coralline district at Exmouth, from which we have obtained 
many live examples. 
A. FERRUGINOSA, nobis. 
Montacuta ferruginosa, Brit. Moll. ii. p.72, pl. 18. f.5, 5a & 5b. 
Mya ferruginosa, Montagu et Auctorum. 
This species has not occurred to us alive, and up to 1849 
all the information obtained from naturalists was, that the foot 
is large, the posterior tubes absent, that it has only a sessile 
orifice, and that the anterior end of the shell is the longer 
side. But since that date, in 1850, we have had the advan- 
tage of seeing Mr. Alder’s paper on the Montacuta ferruginosa 
in the ‘ Annals of Natural History,’ N.S. v. p. 210, pl. 6. f. B. 
We collect from the account, that the mantle of the animal 
is considerably produced anteally, and frmged for a large por- 
tion of its extent. A comparison of these pomts with our own 
notes on the Anatina bidentata, which authors style Montacuta 
bidentata, of which we have examined many live examples, 
shows the concordance of the two species ; in both, the anteally 
produced and frimged mantle, the character of the foot, and 
