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Part III. — Seventeenth Annual Report 



branches of the fourth pair are stouter than those of the outer branches 

 of the same pair in that species. The terminal spines are also slightly 

 different (figs. 5, 6). The fifth pair appears to be wanting in the female. 

 The abdomen is, proportionally, scarcely so long as that of Scolecithrix 

 hibernica. The first segment is about equal to the combined length of 

 the next two, and is rather more dilated ; the second segment is some- 

 what shorter than the third ; but the length of the third and fourth is 

 about equal. The caudal furcae, which are about as long as broad, are 

 somewhat longer than the segment to which they are articulated, and the 

 furcal setae are long and plumose (fig. 8). 



Description of the Male. — The male of Scolecithrix pygmcea resembles 

 that of Scolecithrix hibernica in several aspects, but differs particularly 

 in the structure of the fifth pair of thoracic feet. In this pair the basal 

 joint is stout, and armed with several curved spines as in Scolecithrix 

 hibernica, but the right branch is more slender, and the first joint of 

 that branch is not so irregular in outline. In the present species the 

 first joint of the right branch becomes gradually but only slightly 

 dilated towards the distal end, and is not produced into a large lobe as in 

 Scolecithrix hibernica ; the second joint is smaller, and proportionally 

 much more slender than in that species ; the marginal thumb-like process 

 is small, and situated near the middle of the joint. The left branch of 

 the present form (fig. 7 1.) is also rather more slender than that of 

 Scolecithrix hibernica, but the process at the distal end of the second 

 joint is somewhat more produced and attenuated. The abdomen consists 

 of five segments. The second, which is rather longer than the first, is 

 about one and a half times the length of the following segment ; the 

 third and fourth segments are sub-equal, but the last is very small ; the 

 furcae are about equal in length to the penultimate segments of the 

 abdomen (fig. 9). Figure 10 represents the fifth thoracic feet of the 

 male of Scolecithrix hibernica for comparison with those of the species 

 now described. The figures of both are of the same magnification. 



Habitat. — Firth of Clyde and Loch Fyne. Not very rare. 



Remarks. — This Scolecithrix has been under observation for a con- 

 siderable time. At first I was inclined to regard it simply as a form of 

 Scolecithrix hibernica, but as it continues to turn up both alone and in 

 company with that species, and as all of the specimens are characterised 

 by the same distinctive features, I think it will be more satisfactory to 

 describe it under a separate name. It is distinctly a smaller species than 

 Scolecithrix hibernica, being scarcely a millerrfetre in length. If male 

 and female specimens of the two species be placed side by side — the males 

 together and the females together — the difference in size is readily 

 noticed. The structure of the fifth thoracic feet of the male, and the 

 structure and armature of the anterior foot-jaws of the female, are 

 characters by which the species may be distinguished ; the lengths of the 

 abdominal segments in both male and female are also proportionally 

 different. 



Centropages typicus, Kroyer. 



1849. Centropages typicus, Kroyer. Nat. Tidskr., (2) ii., 

 p. 588, t. 6. 



This species appears to be much rarer in the Clyde than Centropages 

 hamatus, for while the latter form occurs in nearly all gatherings 

 collected in August and September last year, I have only three records 

 for Centropages typicus. On the East Coast of Scotland Centropages 

 typicus appears to be more common. In a series of gatherings from the 



