318 TELLINID^. 



their bases, and are eminently elastic both longitudinally 

 and laterally ; when fully extended they are cylindrical, 

 and very little short of the length of the shell : the animal 

 has the power of inflating them to three times their ordi- 

 nary diameter ; they are of a light brownish colour, the 

 eifect of an epidermis, which, when the tubes are half 

 exserted, exhibits in the branchial and rather longer one 

 about thirty-five annular corrugations, and in the anal 

 twenty-five ; the colour of the true tubes under this epi- 

 dermis, which is sometimes obsolete, is very pale whitish- 

 yellow ; their epidermic cases are prolongations of the 

 investment of the shell ; the branchial tube is truncate 

 and plain at the orifice, the anal furnished with a tubular 

 hyaline valve. The foot is compressed and muscular, large 

 in proportion to the animal : it presents no trace of a 

 byssal groove. The ventral portion of the body is marked 

 with intensely flake-white polymorphous spots ; its dorsal 

 range is chiefly occupied by the liver, which appears of 

 a green colour through its investing membrane ; the 

 branchise are white, two on each side of the body. 



The Syndosmya alba is a very plentiful shell in most 

 sandy and muddy localities around all our coasts, and is 

 so generally distributed that all our maritime provinces 

 may rank it among their inhabitants. It often occurs 

 gregarious in considerable numbers, and is frequently cast 

 on shore. It ranges from one to forty fathoms, and is 

 most abundant in between ten and fifteen. The localities 

 which have furnished the finest specimens are Deal Voe 

 in the Zetlands (Jeffreys) and Loch Long (M'Andrew). 

 It ranges throughout the European seas from Norway 

 to the Mediterranean, and as a fossil commences its ap- 

 pearance in the coralline crag. It lived within our area 

 also during the pleistocene epoch. 



