8 ZOOLOGY OF THE VOYAGE OF H.M.S. SAMARANG. 



Figures 5 and 6 give a view of the mantle of the specimen here described from the dorsal 

 aspect : the anterior aperture of the mouth is trilobed, the lobes obscurely pointed ; one, a, 

 projects forwards from the middle of the dorsal aspect, the two others, b b, from the ventro- 

 lateral aspect, on each side of the base of the funnel, c. Some lacerated remnants of the 

 retractor muscles of the head also projected from the aperture of the mantle, as figured at 

 e, fig. 1 ; but these are omitted in fig. 3, as they obscured the view of the funnel or expiratory 

 tube, c: letters del are the lateral terminal lobes of the mantle applied over the inner whorls 

 and umbilicus of the shell {ch). The ventral aspect of the specimen, fig. 4, shows the 

 beginning or narrower part of the last whorl of the shell as it first protrudes from between 

 the lateral terminal lobes of the mantle, d d. The two ventro-lateral anterior lobes are shown 

 at b b, and the funnel (c) projecting between them : behind this is the torn portion of the 

 muscles of the head. 



The side view of this specimen, fig. 1, shows the greater antero-posterior diameter of the 

 mantle as compared with the transverse diameter in fig. 4 and 5. It also shows the free 

 termination of the shell at/, and the rounded contour and extent of the terminal lobe, d. 

 This part was subjected to a careful and minute scrutiny, but no signs of laceration could be 

 detected : it presented a thick convex border like the bottom of a bag or sac on both sides 

 of the shell (see the magnified view in fig. 11); this border being, as it were, tucked up or 

 bent in towards the umbilicus ; becoming thin and smooth and of a softer texture next the 

 shell, as shown in fig. 7, d and <?, which gives a view of the hinder extremity of the specimen, 

 with the lateral terminal mantle-lobes drawn a little away from the shell to show the delicate 

 portion of the pallial membrane, e, which passes from one lobe to the other through the 

 umbilicus. 



The ordinary surface of the mantle is smooth. Its structure, like that in other di- 

 branchiates, presents a delicate epiderm, a thin stratum of pigmental cells, and a fibrous 

 muscular corium forming the chief substance of the mantle. The dorsal part of the mantle 

 shown in fig. 5, was continued from the anterior pointed lobe, a, backwards to beneath the 

 open end of the shell at fn. fig. 2 ; where it thinned off to the border of a small aperture 

 through which projected the dorsal part of the shell ; there was a small space between this 

 whorl and the anterior border of the aperture, through which aperture the membranous 

 siphon (sk) was continued from the shell into the cavity of the mantle. The aperture seemed 

 much too small to have ever admitted the termination of the shell, f: but it is to be 

 presumed that after the natural connections of the last chamber of the shell with the muscular 

 retractors of the head had been violently disturbed, the mantle may have contracted at 

 the rent, from which the open end of the shell was withdrawn, to the dimensions of the 

 aperture that now admits only the siphon. Nothing at least can be safely argued against 

 M. de Blainville's description of the muscular attachments of the Spirilla to its shell from 

 the obviously mutilated specimen here described. A small part of the second whorl of 

 the shell was visible at the aperture, fn. 



