144 LITTORINIDiE. 



breadth ; in these (perhnps tlistovted) indiviclnals, the 

 moutli was remarka])ly projecting. 



The animal varies in colour from a dull translucent 

 white through every shade of dusky to nearly black. The 

 muzzle is large, rather quadrate, subbilobated in front ; it 

 is often marked with three dark longitudinal lines and is 

 margined with defined black. The tentacles are long and 

 setaceous, of a dull white or yellowish hue, with a black 

 spot or bar at a short distance from their extremities ; the 

 eyes are large, black, and jirominent on bulgings at the 

 exterior bases of the tentacula. The foot is squarish, 

 angled obtusely in form, rounded posteriorly (and, accord- 

 ing to Mr. Clark, sometimes emarginated) ; the caudal 

 part extends considerably behind the operculum. The 

 caudal filament is aborted. The above description, which 

 will be found to agree in all essential points with those 

 published by Mr. Berkeley and Mr. Clark, was drawn up 

 from specimens gathered at Glengarilf in the south of 

 Ireland. 



" These animals," observes Mr. Clark, " creep with 

 great rapidity, and float Avith the foot uppermost by means 

 of a hydrostatic apparatus, as air-bubbles are seen con- 

 tinually to proceed from the aperture ; they are strictly 

 littoral, and inhabit in myriads the green oozes of 

 estuaries." * 



This common Mollusk is found in all brackish water, 

 and estuary localities between tide marks round the British 

 Isles, where it is a favourite food of water-birds. 



The Rissoa Barleei appears to be undistinguishable 

 though found in so different a locality, having been 

 dredged by Mr. Barlee and Mr. Jeffreys in twenty to 

 forty fathoms, Loch Carron and Skyo. 



* Annals of Natural History for May, 1850, p. ,3.58. 



