222 kelliid^:. 



diately fixes itself, when placed in a basin of sea- water,, 

 by its threadlike byssus. The foot protruded, but not 

 in action, occupies a central position : it is usually pushed 

 through the slit at the base of the tube on the anterior 

 side when the animal wishes to move forwards, and, fixing 

 itself by a kind of suction, rapidly draws the shell after 

 it ; and it can also execute a similar movement backwards, 

 but more slowly. The animal never remains long with- 

 out forming a byssal attachment ; but when inclined to 

 move, it seems to have no difficulty in slipping its cable, 

 which is always discarded and left in situ. The surface 

 of the shell is sometimes coated with confervoid spores, 

 giving it a greenish appearance. My largest specimens 

 are from Shetland. 



Walker first noticed and figured this species in his 

 account of minute and rare shells from Sandwich ; but 

 his description was excessively meagre, and no specific 

 name was added. It is in all probability the Amphi- 

 desma nucleoid of Lamarck, Erycina violacea of Scacchi, 

 Cycladina Adansonii of Cantraine, Erycina Fontenayi of 

 Mittre, and Bornia seminulum of Philippi. Stimpson 

 remarks that the Kellia rubra of Gould is not our spe- 

 cies, having a more compressed form and much smaller 

 beaks. He therefore gave the name of planulata to the 

 North-American species. Gould's figure seems to re- 

 present Montacuta bidentata. 



Genus IV. KEL'LIA*, Turton. PL V. f. 3. 



Body globular : mantle folded on the anterior side (being the 

 shorter and smaller end of the shell), so as to form a bag-shaped 

 incurrent tube, and folded on the opposite side into an excur- 

 rent tube, which is more prominent but shorter : gills two, sym- 



* Named after the Rev. J. M. O'Kelly of Dublin, a conchological asso- 

 ciate of Dr. Turton. 



