British species of Naked Mollusca. 291 



two lobes, which meet in the medial line behind. This is not ex- 

 actly the case with ours, but the front is very variable in outline, 

 according to the will or position of the animal ; and as it is a little 

 sinuated in the centre, it frequently assumes a bilobed appear- 

 ance, and the line of white spots mentioned above gives an appa- 

 rent continuation of the outline of the head across the medial 

 line, similar to what is represented in M. de Quatrefages' figure. 

 The form of the cloak and the dark line passing from it to the 

 tail are the same in each. On turning to the internal charac- 

 ters we find the same peculiar gizzard, or dental armature of the 

 stomach, as described in the French species, and some of the 

 other parts are not very dissimilar. But M. de Quatrefages 

 states that his genus Pelta has neither branchise, heart nor anus, 

 thus reducing it to a level with the inferior zoophytes. We must 

 confess that we have always looked upon this extreme degradation 

 of the Molluscan type with great suspicion, and the discovery of 

 this species has tended not a little to strengthen our conviction 

 that M. de Quatrefages' views are founded upon imperfect ob- 

 servations. We cannot indeed prove that our mollusk belongs 

 to the same genus as the Pelta ornata, but sufficient has been 

 stated to raise a presumption that it does so; and considering the 

 great difficulty of examining these minute objects anatomically, 

 the inability to detect an obscure organ must not be hastily taken 

 as a proof of its non-existence. Indeed in one or two of the 

 smaller specimens of our mollusk, we were ourselves unable to 

 detect either branchial plumes or anal aperture. The latter we 

 have no doubt existed ; but with regard to the former, we think it 

 probable that these animals in a young state undergo a progres- 

 sive development, and that it is not until they have arrived at 

 maturity that the branchial organs are fully developed, respira- 

 tion in the meantime being carried on chiefly through the ciliated 

 surface of the body. 



There is yet another mollusk to which our species bears a very 

 strong resemblance, — the Limapontia nigra of Dr. Johnston, de- 

 scribed in Loudon's Magazine of Natural History, vol. ix. p. 79. 

 The figure there given is a pretty fair representation of our ani- 

 mal, and the colour appears to be the same. Dr. Johnston was 

 unable to detect any branchise, and the cloak, though mentioned 

 as distinct from the foot, is not so represented in the figure. It 

 is possible, however, that the species may turn out to be identical. 



Were we inclined to construe generic characters rigorously, 

 we should be quite justified in establishing a new genus for an 

 animal so differently organized as we have shown this to be ; but 

 believing as we do that we see in our little mollusk the repre- 

 sentative of two genera already described by naturalists, though, 

 camelion-like, when again produced it turns out to be something 

 different from what either party had supposed, we shall leave it 



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