TESTACEA. 39 



A black eye is on the external margin of each socket. The sole is a 

 long oval. From each side of it issue three long slender tentacula, organs 

 which testify a searching action, as is exhibited also by the real tentacula. 

 A kind of fringe or cloak, somewhat resembling that of the Doris, projects 

 a little from the body over the sole. 



This animal feeds on the CoraUina officinalis, both in its earlier and 

 maturer state. It seems more common on the shore of some ]ilaces where 

 that product abounds. It is very lively, restless, and impatient ; prone 

 to quit the water, and crawl out of its vessel. 



The observer will frequently see two slender, white, tentacular organs 

 issuing from the vertex of the shell, and playing around it. But these are 

 foreign to the animal : they are the tentacula of a species of Spio, nest- 

 ling in a cavity there, which has been perhaps formed by accident, or by 

 decay of the shell. 



Plate VIII.' 



Fig. 1. Trochus cinerarius, viewed from above. 

 2. Under surface. 



2. Trochus zizvphinus. — Plate VIII., Figs. 3, 4, 5. 



Height of the shell, an inch ; diameter of the largest volute, an inch : 

 figure quite conical ; volutes about six, each composed of smaller portions ; 

 colour reddish orange, finely speckled by a row of minute spots in tlie 

 middle of each volute. 



The animal resembles generally that of the Trochus cinerarius. Total 

 length above an inch and a quarter ; head very distinct, sole broadened 

 at the shoulder, lower extremity obtuse. Six tentacular organs issue from 

 the sides, as in the Trochus cinerarius. Tentacula two, extending half an 

 inch in large specimens, slender, a black eye at the external root of each ; 

 colour yellowish. 



This animal feeds on Zoophytes, as the Sertularia rosacea, and also 

 on the common green fucus. 



It is restless, and seeks the highest part of its vessel. 



