116 LITTORINID^. 



suture, but do not extend to the lower one. 

 Whorls seven, almost smooth (at most very 

 obscurely subcancellated), but almost always with 

 some obscurely raised spiral lines that are here and 

 there perceptible : lip rarely marginated, pillar 

 sometimes coloured (pi. LXXXII. f. 7, 8). This 

 form, especially where the lower set of streaks 

 unite at the base of the body into a spiral zonci 

 closely resembles the B>.parva, var. interrupta, from 

 which the straightness of its pillar-lip, its more 

 ventricose whorls, the obscure traces of spiral 

 sculpture, and the absence of the characteristic 

 dorsal painting of the outer lip suffice to dis- 

 tinguish it. 

 Var. D. (? similis of Brown). Elongated thin; lower 

 whorls almost smooth ; upper ones with a few 

 strong longitudinal ribs (pi. LXXXII. f. 9.) 



Mr. Alder has examined and described the animal of 

 this species. It is " white, with two long setaceous 

 tentacula, having the eyes at their external base. Head 

 bilobed. Foot slender, produced in front, white, with a 

 black spot in the centre of the posterior part. The sides 

 have two lobe-like appendages, margined with dark purple 

 or black : two other lines of the same colour, on each 

 side, run parallel to these ; the upper one on the side of 

 the back, the lower bordering the foot. The rest of the 

 body is white, with some blotches of yellow.* 



The animal of the form tenuis, found sparingly by Mr. 



Alder at, and a little below, low-water mark, at Rothsay, 



is described by him as having " the head umber-brown 



above, the muzzle not quite so much produced as usual, 



* Annals Nat. Hist. vol. xiii. p. 324. 



