MOLLUSCA OF PLYMOUTH SOUND. 187 



Monograph, Synopsis, p. 47, " brancliise forming a nearly continuous 

 waved line of papillae on each side/') The dorsal tentacles had the 

 same form as in L. marmoratus and were completely retractile within 

 their sheaths. Each sheath was long, stout, and produced at the 

 margin into Jive or six blunt prominences or tubercles. It is thus 

 seen that this animal differs from Alder and Hancock's marmoratus 

 almost exclusively in the form of the tentacular sheaths and in the 

 colouring ; and the doubt arises whether Alder's view of specific 

 characters in this genus can be any longer regarded as correct, since 

 upon it a new species ought to be created for the reception of the 

 iudividual just described. 



As was apparently the case with the Weymouth examples, our 

 two other specimens agreed so closely that a single description will 

 serve for both. Length half an inch. Colour much darker than in 

 the preceding specimen, being of a rich, dark, velvety brown, 

 spotted profusely with yellowish white. Veil with four blunt but 

 prominent processes, thicker than in the preceding. Epipodial ridges 

 on each side well marked, thick, fleshy, and foliaceous, undulating 

 four times (four in, four out), the margins beset with bulbous papillae 

 of which the median ones of the inward undulations were longer 

 than the rest. The outward undulations were as well marked as the 

 inward. Tentacular sheaths spacious and fleshy, each with five 

 projections on the margin. Foot exceedingly narrow and slender, 

 to some extent at least from contraction. On the morning of June 

 12th each of these individuals had a couple of pieces of spawn upon 

 its back behind the tentacles. Each piece was in the form of an 

 incomplete coil, thickened at the commencement, and in shape much 

 resembling a comma (o ), the tail being taken, however, rather closer 

 round the head. The two pieces were placed with the " heads " close 

 together and " tails " approaching each other, one of the commas 

 being reversed (oc ), and were guarded in this position by the first 

 pair of inward undulations of the epipodial ridges which approached 

 above so as to touch each other in the mid-dorsal line (cf. L. port- 

 landicus). The chief peculiarities common to these two specimens 

 were the dark brown colour, the thick fleshy character of the papillae 

 (which reminded me of the condition in JEgirus punctilucens) , and 

 the very slender foot. The fact that these two individuals should 

 present such a close agreement in almost every point (in alcohol one 

 has not quite so much brown pigment as the other) and that the differ- 

 ences between them and the other described British examples of the 

 genus are comparatively considerable, would have been quite sufficient 

 reason for the creation of a new species if I had not paid some 

 amount of attention to the question of variation in the group generally. 

 In my notice of Tritonia plebeia [supra] I described one or two 



