474 ALATID^E. 



ROSTELLARIA, Lamarck. 



R. PES PELECANI, Lamarck. 



Aporrhais pes pelecani, Auctorum. 



, Brit. Moll. iii. p. 188, pi. 89. f. 4 ; (animal) 



pi. I.I. f. 3. 



Animal occupying an elongated,, alated, pale red-brown, 

 finely spirally striated, nodosely ribbed shell of 1214 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 papillae, 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 pink and flake-white dots, 

 which resolve themselves into a linear aspect at the sides j 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-pointed, carrying at its extremity, 

 on a small plain oval lobe, a minute, somewhat elongated, irre- 

 gular-shaped, darkish brown, horny operculum, which entirely 

 resembles that muricidal organ. The foot is white beneath ; 

 above also white, but sprinkled sparingly 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 manosuvre many 

 times, and apprehend that in freedom it can only thus reverse 

 its position. 



