2 84 Shell Life 



half an inch in length, white, and almost transparent, 

 covered with stalked tubercles that mimic the closed 

 tentacle-crowns of certain pol3^ps. Most of the twelve 

 British species of this genus have similar tubercles, 

 and it is therefore not surprising to find that several 

 of them have been taken in the act of feeding on 

 Polyzoa which they resemble in colour and markings. 



The Angled Doris {Goniodoris nodosa) is about 1 

 inch in length, of a transparent white colour tinged 

 with rose and sprinkled with opaque white or yellow 

 dots. The mantle has a wavy margin, and at the 

 rear it is cut into a number of cusps which suggest 

 the name. A second species, G. casianea, is somewhat 

 smaller, of a reddish-brown tint usually, covered with 

 soft tubercles which are blotched with ^^ellowish 

 white. This species feeds upon colonies of Compound 

 Ascidians (Botryllus), and when so engaged is very 

 inconspicuous. 



The Venus Slug {Idalina elegans) is obviously got 

 up to look like a beautiful anemone. It is about 

 Ih inches lono-, the back much more elevated than 

 usual, of a delicate pale-rose tint speckled with 

 a deeper shade. The edge of the mantle is drawn 

 out into a number of filaments of an orange colour 

 with yellow tips. The foremost two of these fila- 

 ments are developed to a large size, and being just 

 below the tentacles look very like an additional pair. 

 The true tentacles and the branchial plumes are all 

 coloured like the mantle filaments, so that they 

 appear to be the waving tentacles of an anemone. In 

 spite of its brilliant tinting Idalina does not, like so 

 many of the Sea-slugs, seek surroundings of similar 

 colour, but goes where it will be highly conspicuous, 



