474 ALATID A. 
ROSTELLARIA, Lamarck. 
R. pes PELECANI, Lamarck. 
Aporrhais pes pelecani, Auctorum. 
—_— , Brit. Moll. ii. p. 188, pl. 89. f. 4; (animal) 
pis. £3! 
Animal occupying an elongated, alated, pale red-brown, 
finely spirally striated, nodosely ribbed shell of 12-14 rather 
tumid volutions. The mantle, of the palest fawn-colour and 
thinnest texture, very extensible, lax and sinuated, can be 
spread over the entire porcellanous area of the inside of the 
aperture, and lines, without becoming a produced siphon, the 
typical branchial canal in the outer lip, and the linear de- 
pressions of the pterygoid processes. The head is a long, 
cylindrical, tapering red proboscis with a yellowish flake-white 
margined disk vertically cloven, aspersed above with very 
minute yellow papilla, and more posteriorly on the neck with 
irregular pink blotches, beneath white, with a few red-brown 
points. The tentacula are slender, of concurrent length with 
the proboscis, and sprinkled with pmk and flake-white dots, 
which resolve themselves into a linear aspect at the sides ; the 
eyes are minute, fixed on short pedicles at the external bases. 
The foot, when extended, is long, narrow, auricled, and con- 
tracted at one-third of the length from the front, rather lanceo- 
late behind, but not sharp-poimted, carrying at its extremity, 
on a small plain oval lobe, a minute, somewhat elongated, irre- 
eular-shaped, darkish brown, horny operculum, which entirely 
resembles that muricidal organ. The foot is white beneath ; 
above also white, but sprinkled sparmgly with pink dots. 
The locomotion is slow ; but though the animal creeps, the 
organs do not appear adapted for progressive movement. It is 
very shy, and whether the shell is placed with the aperture 
upwards or downwards, it does not usually commence creep- 
ing by pushing out the foot anteriorly, like other Gastero- 
poda, but often twists the long neck and foot to the caudal 
extremity, and there fixing it, with a sudden spring effects 
the turning of the shell. I observed this manceuvre many 
times, and apprehend that in freedom it can only thus reverse 
its position. 
