LACUNA. M7 



wide, expanded outwards and below, slightly angular at the 

 base : outer lip very thin, occasionally strengthened a little 

 way inside by a slight white rib or callus : inner lip also thin, 

 united with the outer lip, and partly covering the canal : 

 pillar white ; canal wide, oblique, funnel-shaped, and exposing 

 a considerable part of the spire : inside polished, of the same 

 colour as the outside : operculum as in L. crassior and similarly 

 sculptured. L. 0-45. B. 0-3. 



Yar. 1. canalis. Without coloured bands, and usually of a 

 thinner texture. Turho canalis, Mont. Test. Brit. p. 309, 

 t. xii. f. 11. 



Yar. 2. quadrifasciata. Smaller, more conical and solid, 

 with a keeled periphery ; outer lip thickened within its edge 

 by an inside rib. Turbo quadrifasciatus, Mont. 1. c. p. 328, 

 t. XX. f. 7. 



Yar. 3. gracilior, Metcalfe. Smaller and much elongated. 



Habitat : Seaweeds and Zoster a, at low- water mark 

 and in the laminarian zone throughout the British seas ; 

 abundant. The first two varieties are also everywhere 

 common; the third was found by Mr. Metcalfe in 

 Guernsey, and by me in Langland bay near Swansea. 

 Fossil in the Clyde beds (Smith and others) ; Fort 

 WiUiam (J. Gr. J.) ; Aberdeenshire ( Jamieson) ; Moel 

 Tryfaen (Darbishire) ; Norwich or Mammalian Crag 

 (S. Wood); UddevaUa (J. G. J.), and 40 feet above the 

 sea (Malm); Christiania district, newer deposits, 100 

 feet (Sars). Its distribution in a living state is mainly 

 northern, and comprises Greenland, the White Sea, 

 Russian Lapland, Iceland, the Faroe Isles, Scandinavia, 

 Heligoland, Normandy, Brittany, and Gulf of Gascony, 

 besides the eastern and western coasts of North America. 



It appears to be the favourite food of many sea-birds. 

 Dr. Saxby took specimens from the stomach of a Black 

 Guillemot at Unst, each of which had the operculum in 

 its usual position, although nearly all the soft parts had 

 disappeared. This is a shy but restless mollusk ; and 



