10 G. 0. Sårs. 



Description of the male. 



The following are the chief dimensions of an apparently 

 fully grown specimen: — 

 Total length, from the frontal margin to the end of 



the last caudal segment l 32 mm. 



ISTedian length of carapace 12 — 



Greatest width of same 14 — 



Length of exposed part of body 20 — 



Length of caudal part 13 — 



Length of caudal filaments 12 — 



Length of the outermost endite of 1st pair of legs 10 — 



It will appear from these dimensions, and from a com- 

 parison of figs. 1 and 4, that the male grows to a larger 

 size than the female, and that the relative proportions of 

 the chief parts of the body are also somewhat different. 



On the whole, the body (see fig. 4) appears considerably 

 more slender, and the carapace smaller in proportion to the 

 exposed part of the body, which is nearly twice the median 

 length of the former. In shape and structure, however, the 

 carapace closely agrees wdth that of the female, exhibiting 

 a very similar cordiform outline, though perhaps a little 

 broader in proportion to its length. 



The exposed part of the body is somewhat less tapering 

 distally, and more regularly cylindric in form, comprising no 

 less than 36 segments, the 18 anterior ones being pedigerous. 

 The other 18 segments are without ventral appendages 

 (see fig. 5), and accordingly belong to the tail, which thus 

 contains 4 segments more than in the female. In no other 

 species of Apus has such a large number of caudal segments 

 ever been recorded. The structure of the segments is other- 

 ivise exactly as in the female. 



