Fah]S'ik. — The Structure of Amphibola crenata Martyn. 



71 



immersed in fresh water but not so sealed up it will live for a fortnight ; 

 if completely immersed in sea-water it will live a month ; but if left with- 

 out any water at all it does not live more than a day. Even when the tide 

 is low there is always a certain amount of water left in the mud, so that 

 these animals are not, in their native habitat, left absolutely dry. 



External Features. 



As Suter gives a good technical descrij)tion and figure of the shell it is 

 unnecessary to deal with it here. 



The animal is of small size and of a beautiful rich black colour. 



The head is but slightly marked off from the foot, and is relatively of 

 great breadth (fig. 2). Its anterior region is rather deeply excavated in the 

 middle line so as to form a pair of lappets, one on each side of the mouth. 

 Some distance from these are situated the pair of small, flat, triangular 

 tentacles, which in the majority 

 are so deeply pigmented that 

 the minute eye is not readily 

 seen, but in paler specimens the 

 eye is recognized as an extremely 

 small black dot of darker pig- 

 ment close to the tip of the 

 tentacle. Quoy and Gaimard, 

 though mentioning the eyes, 

 failed to note the tentacles. 

 Hutton (1879), however, de- 

 scribes the latter, but states that 

 the eye is at the base. This 

 error is repeated, naturally, in 

 Suter's Manual, but any one 

 who examines the creature with 

 sufficient care will be able to 

 confirm my statement."^ 



The foot is short, and almost 

 circular in outline, as seen from 

 below (fig. 1). In preserved spe- 



cimens it is very much shrunken, 

 but if examined when the animal 

 is walking it will be seen that the 

 foot is capable of being expanded 

 until a narrow margin is visible 

 beneath the shell all the way 

 round except on the right side. 

 The foot is separated from the 

 head by a slight furrow ; there 

 is no distinction into pro-, 

 meso-, and meta- podium, nor 

 have I found any trace of a 

 creeping-sole is cream-coloured 



Fig. 2. — Dorsal view, of the animal removed 

 from the shell { X 2). The foot is bent 

 upon itself so that the ventral surface of 

 its posterior region is seen in front of the 

 head. Some of the interior organs are seen 

 by transparency, e, eye ; cj, groove into 

 which anus opens ; gp, genital pore ; gz, 

 gizzai'd ; int. intestine ; ipl. inferior jiallial 

 lobe ; k, kichiej^ ; m, mouth ; mc, collar ; 

 pa, pulmonary aperture ; rl, right lappet 

 of head ; t, tentacle ; vf, ventral surface 

 of foot. 



pedal gland. The anterior part of the 

 the posterior part greyish-blue. 



* It is not surprising that the tentacles were overlooked by the earlier zoologists, 

 if they had only preserved specimens at their disposal, for when the head is contracted 

 they are difficult to distinguish from wrinklings of the body-wall. As to the eye, in 

 ordinary specimens they, too, are indistinguishable in such material : it is only in fresh 

 specimens and in those in whicli the pigmentation at the tip of the tentacles is less than 

 usual that they can be seen. [W. B. B.] 



