ws) 
or 
i) 
RISSOA. 
Lirrortna vincta, Montagu. 
L. vineta, Brit. Moll. iii. p. 62, pl. 72. f. 10, 11,12; pl. 74. f.7, 8; 
pl. 86. f. 6, 7, 8; (animal) pl. G.G. f. 4. 
Lirtrortna crasstor, Montagu et nobis. 
Lacuna crassior, Brit. Moll. ui. p. 67, pl. 72. f. 5, 6. 
RISSOA, Freminville. 
R. utv#, Pennant. 
R. ulve, Brit. Moll. iii. p. 141, pl. 81. f. 4, 5,8,9; pl. 87. f. 2,8; 
(animal) pl. J.J. f. 8. 
R. subumbilicata ?, Montagu. 
, Brit. Moll. i. p. 137. 
Animal spiral, of 6-8 volutions ; mantle plain; bead a long 
dark proboscidiform muzzle, emarginate in the centre in front, 
marked with two transverse bars, and its margins edged with 
the same dark colour; buccal disk pale brown or yellow, with 
a vertical fissure, from which, when the animal gapes, a pair of 
curved jaws are seen; these are the anteal termination of the 
lingual riband, which makes its way to the stomach through a 
pair of fleshy, or rather horny, plates, the whole forming what 
is called the masticatory apparatus ; tentacula very long, cylin- 
drical, slender, pointed, very little setose, whitish-yellow, with 
a black bar at a short distance from their termini; eyes at the 
external bases on short protuberances; foot short, truncate 
and auricled in front, rounded, and, in some individuals, 
slightly emarginate posteriorly. In the lighter coloured 
variety, the upper part is a pale brown, beneath yellowish- 
white, with a border of minute pale golden flakes, with some- 
times a dark bar running through the centre of its posterior 
part; in the darker variety, the upper part of the foot is 
clouded with very fine dark lead-colour to its paler hues, 
underneath pale brown. 
These animals creep with great rapidity, and float with the 
foot uppermost by means of an hydrostatic apparatus, as air- 
bubbles are seen continually to proceed from the aperture ; 
they are strictly littoral, and inhabit im myriads the green 
oozes of the estuaries. 
2A 
