CIIEMNITZIA. 247 



What we temporarily regard as the southern form is a 

 rather stronger and larger shell (one we dredged at Wey- 

 mouth measures half an inch in length, and the tenth of 

 an inch in breadth), is of an uniform pale rufous tint, and 

 has from twelve to fourteen still flatter whorls, and quite 

 straight ribs, which vary in number and thickness upon 

 different specimens. The form too is very variable, being 

 slender in some individuals, whilst in others it is shorter, 

 and tapers more suddenly from a broader basal volution. 

 The intervals between the spiral lines upon the base are 

 occasionally elevated into obtuse costellse. 



The animal is entirely white. Its tentacles are ob- 

 tusely lanceolate, rather broad, set well apart, and having 

 their eyes at their bases a little on the inner side. The 

 foot is oblong, truncated, with slightly obtuse angles in 

 the front, obtusely and rapidly triquetrous behind. The 

 mentum is bilobed, narrower than the foot, and angulated, 

 but not acutely. In crawling the animal advances both 

 mentum and foot much in front of the head, and the 

 former often foremost. 



This beautiful shell, although but recently defined as a 

 native species, having first been distinctly recorded by Mr. 

 W. Thompson, is very generally distributed around our 

 coasts, occurring on all sides of the British Islands, usu- 

 ally, however, sparingly. It inhabits a bottom of sand or 

 sandy mud, usually in from fifteen to thirty or forty fa- 

 thoms water, but Mr. M 'Andrew has dredged it in as deep 

 as ninety fathoms off the Zetland Isles, and Mr. Jeffreys 

 in as little as eight fathoms at Fishguard. The original 

 specimens found by Miss Mary Ball at Portmarnock, were 

 taken, we believe, from shell sand. 



It ranges from the coasts of Scandinavia, where it has 

 been taken by Loven, to the Mediterranean sea. 



