Dr. Johnston on the Irish Annelides. 179 



stinct, rather small, obtusely triangular; the antennae minute 

 and shorter than the palpi ; proboscis large, destitute of all 

 horny prickles, but armed with powerful jaws, which are only 

 faintly serrulated near the base. Post-occipital segment not 

 larger than the second : tentacular cirri short, not so long as 

 the breadth of the segment. Segments very numerous : feet 

 of the anterior pairs with 3 rather long papillary and equal 

 branchial lobes, the dorsal cirrus not reaching much beyond 

 their apices ; but the posterior feet much resemble those of 

 N. renalis. 



Although the size of an animal is not usually reckoned a 

 good specific character, yet we know that every species has in 

 this respect certain limits which it never either much exceeds 

 or falls short of. For this reason it seems to me impossible 

 to regard Nereis longissima as a variety of N. renalis, notwith- 

 standing the similarity in the structure and figure of the feet 

 would induce that belief; and I have been fain to resort to the 

 distinctions afforded by the jaws and proboscis for their separa- 

 tion. This is the only known species with a prickless proboscis, 

 and the serratures of the jaws are likewise fainter than in any 

 other I have examined. As the specimen of N. longissima is 

 not in a good condition, some allowance will be made, should 

 the outline given of the posterior foot be found not wholly 

 exact, but I am confident that the general contour and pro- 

 portions are accurately expressed. 



Before I examined this worm I had mistaken it for a spe- 

 cies of Phyllodoce, which it more resembles in size and gene- 

 ral aspect than a Nereis, and it is obviously a transition spe- 

 cies, proving the affinity of these two genera. The foliaceous 

 lamellae of the feet are quite similar in structure to the branchial 

 leaflets of the Phyllodoce, and from the manner in which they 

 are veined, are evidently also branchial in their function. 



N.B. The numbers affixed to the figures express the number of the seg- 

 ment from which the foot was taken that served for the figure : m means 

 that the foot was from near the middle ; and p from near the posterior ex- 

 tremity of the body. 



[To be continued.] 



