LACUNA. 345 



cealed by the epidermis : colour yellowish with a faint tinge 

 of b^rown ; the apex is sometimes of a darker hue : epidermis 

 membranous ; it is usually puckered lengthwise into irregular 

 folds, and it is most commonly rubbed off or absent on the 

 top of the shell : sinre more or less raised, terminating in a 

 blunt point : ivJiorls 6-7, rather convex but compressed, some- 

 what angular above, and gradually increasing in size : suture 

 deeply excavated : mouth rather large, considerably exjianded 

 below and angulated at the base: outer lip very thin and 

 fringed by the epidermis, incurved above on the pillar side : 

 inner lij) filmy, spread over the lower part of the body- whorl, 

 and partly covering the canal when present ; it is not united 

 with the outer lip : pillar white, sometimes faintly tinged with 

 pink ; canal or groove more frequently wanting, but when 

 existing it is rather wide, oblique, and ends in a small but 

 deep perforation : inside porcelain-white and polished : oper- 

 culum having 5 or 6 whorls, the outermost of which occupies 

 nearly the whole area, the others being disproportionately 

 small ; it is marked across with curved lines of growth, and 

 lengthwise with microscopical and close-set striae, which last 

 radiate from the nucleus. L 0-5. B. 0-3. 



Habitat : Among stones and old shells in sandy 

 ground mixed with mud, from low- water mark to con- 

 siderable depths, on all our coasts, including the Chan- 

 nel Isles and Shetland ; it is rather local. Mr. Grainger 

 has recorded it as fossil from a deposit at Belfast. I 

 found it at Etretat, in Normandy ; and what I consider 

 a variety of L. crassior, connecting it with L. divaricata, 

 has been described by MoUer as a Greenland shell under 

 the name of L. glacialis. MiddendorfF gives the White 

 Sea, coasts of Russian Lapland, Sea of Okhotsk, and 

 Sitka Island as habitats of the present species and of 

 the variety glacialis. 



The animal is active, hardy, and seemingly fond of 

 getting out of the water. Mr. Dawson has observed 

 that it moves at the rate of about two inches per minute ; 

 as it progresses the shell is carried along at a slow 

 swinging pace. This arises from the peculiar action of 



Q 5 



