404 THE OPlSTHOBRANCeiATE 



Markings. — The markiDgs of our specimens I have studied only in 

 the preserved condition. In some of the smaller specimens no 

 markings at all are to be observed, but as others pi'eserved in the 

 same way show very conspicuous markings it is probable that con- 

 clusions drawn from these preserved specimens are valid. The 

 largest of the small specimens in which markings are absent, measures 

 If inches long in a fair state of extension. Where present, the 

 marking of the integument is always due to small grey dots, either 

 pale or dark, slightly elongate in form, which may be grouped in 

 various ways. They may be evenly dispersed over the whole of the 

 integument, forming no rings and leaving no clear spaces, or, though 

 arranged in the same way, may be distributed over only a limited 

 portion of the integument, viz. on the back of the head and on the 

 upper portion of the sides of the body. It is, indeed, generally the case 

 that, as Brock has described for ^. ptmc^afa (Blochmann,l. c, p. 34)7 

 the marking does not extend to the foot and inner side of the pleuro- 

 podia, but is limited to the upper surface of the body. The most 

 usual type of marking, however, consists in the dots being so dis- 

 tributed (either over the whole surface of the integument or over 

 the upper portion only) as to leave round or elliptical clear spaces 

 from which all markings are absent. The spaces may be either 

 definitely bounded by a close series of dots or not very definitely 

 bounded ; there is every gradation between these two conditions. 

 The former of these conditions is represented in Mrs. Gray's Figures 

 of Molluscous Animals, vol. ii, pis. cxxxviii, cxxxix, and cxlii, both for 

 A. dep'ilans and A. punctata; the latter condition is shown on 

 pi. cxlii"^ for A. depilans. The dots in most specimens show a 

 great tendency to be arranged in a certain order, either in straight 

 or curved lines, or in the form of hexagonal, circular, elliptical, or 

 irregular markings, enclosing clear spaces of small diameter. But 

 there is every gradation between these small dot-bounded spaces 

 and the large ones mentioned above. In a number, though not the 

 majority, of individuals, the dots enclosing these small circular spaces 

 may be so continuous as to produce very definite ring-like spots. 

 These are chiefly to be found on the head anil neck, and more rarely 

 on the sides of the body. In our largest specimens the marking 

 consists largely of a reticulum formed by lines of pigment-dots run- 

 ning in all directions, crossing one another and anastomosing, here 

 and there leaving large or small clear uupigmented spaces, with in- 

 definitely bounded edges. 



So far as the marking is concerned, therefore, some of our smaller 

 specimens have the positive characters of A. punctata as described 

 by Blochmann and Yayssiere ; but many of the smaller ones, as well 

 as all the largest ones, could equally well be placed — so far as the 



