220 POPULAR BlUTISH CONCHOLOGY, 



creeping. It is of an olive or yellowish- grey tint^ speckled 

 with brown, varied with spots of white. The two front 

 tentacles are long and half-tubular, the two hinder ones 

 short and pointed ; the small black eyes are placed at the 

 base of the tentacles. 



The shield, or shell, is transparent, thin, brown, liorny ; 

 the outside is convex, and the apex shows scarcely the rudi- 

 ment of a spire. 



The British sea-hare lives and lays its slimy nests of eggs 

 among, and partly feeds upon, seaweeds below low-water 

 mark. 



II. Pleurobranchus, the one genus of PleurohrancJiidcs, 

 has a very delicate, fiattish, membranaceous shield, which 

 protects, not, as in Aplysia, the breathing apparatus, but 

 the viscera of the body. The breathing apparatus is partly 

 free, and consists of a single plume. The animal on the 

 whole resembles the Aplysia in general appearance, but 

 more rounded when at rest. Of the two British species, 

 the shield of 



P. memhranaceus is broad and squarish, while that of 

 T.pliimida is narrow, more shelly, and small, with a rather 

 more coiled apex : it is a comparatively rare species. 



