NO. 5.] ACCOUNT OF THE SPECIES. 121 



length the caudal segments and the last segment of the trunk combined, lateral 

 seta occurring at the end of the first 5th part of the ramus. Anterior antenna; 

 fully as long as the anterior division of the body, and composed of only 3 

 distinct joints clothed with very strong setae, which, as a rule, issue from cup- 

 shaped ledges; 1st joint somewhat longer than the other 2 combined, the 

 latter about equal in size. Posterior antennae with the outer ramus about the 

 length of the proximal joint of the inner, and 7-articulate. Outer ramus of 

 the 3 anterior pairs of legs distinctly 3-articulate, that of 4th pair biarticulate; 

 inner ramus of 1st pair 3-articulate, of 2nd pair biarticulate, of 3rd and 4th 

 pairs uniarticulate. Length of adult female 1'38 mm. 



Remarks. As mentioned above, this form seems to be closely allied to 

 one of the species recorded by Dr. Giesbrecht, viz., M. minor. Of this 

 species, however, only 2 detail-figures have been given (a posterior maxilliped 

 and a 2nd leg), and it is therefore as yet scarcely possible to institute any 

 closer comparison between these 2 forms. 



Description of the Female. 



The length of the body, measured from the front to the end of the 

 caudal rami, is 1'38 mm. Dr. Giesbrecht gives the length of his M. minor 

 as 1-25 1 - 35 mm., and that of M. phasma as 1'58 1'73 mm. 



The whole body, even in the preserved state, is so perfectly hyaline, that 

 it was a matter of no little trouble to pick up the specimens from the 

 sample. The general form of the body (see figs. 1 & 2) is slender and elon- 

 gated, with no very sharp demarcation between the 2 chief divisions, though 

 the posterior is much narrower than the anterior. The latter division is 

 somewhat depressed, especially in its anterior part, and, seen dorsally (fig. 

 1), exhibits an oblong fusiform shape, with the greatest width not attaining 

 Va of the length, and occurring considerably in front of the middle. It gra- 

 dually tapers behind, somewhat less in front, and has the anterior extremity 

 obtusely truncated. The cephalic segment is well defined, and occupies about 

 2 /B of the length of the anterior division. Seen laterally (fig. 2), the dorsal 

 face of this segment declines obliquely towards the front, which appears 

 narrowly rounded, and slightly deflexed between the insertions of the anterior 

 antennae. The 1st pedigerous segment is rather large, exceeding in length 



the 2 succeeding segments combined. Tho penultimate segment is only very 



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