327 



Occurrence. I have seen only 2 female specimens of this remarkable form, 

 taken many years ago off the west coast of Norway, the exact locality not being 

 noted. One of these specimens, the one here figured, was provided with greatly 

 developed ovarial tubes, the structure of which seemed to differ conspicuously 

 from that generally found in this group of Copepoda. As seen from the 2 habitus- 

 figures here given, in which these organs are represented as exactly as possible, 

 the posterior parts of the tubes extending through the urosome are greatly dilated 

 and contain each 4 large ovarial cells lying end to end, and exactly corresponding 

 in the 2 tubes. At the junction of the anterior and posterior divisions of the 

 body, or more correctly in the anterior part of the genital segment, the tubes 

 become abruptly contracted, lying also somewhat more dorsally, and the enclosed 

 cells rapidly diminish in size anteriorly. It is very probable that the large ovarial 

 cells in the caudal part were ready to be discharged from the genital openings, 

 to form 2 separate ovisacs, each with 4 ova arranged in a single row. Ovigerous 

 specimens- of this form have not, however, as yet been observed. 



Distribution. Scottish coast (Scott). 



Fam. 17. Tachidiidae. 



Characters. Body of somewhat varying shape, in some cases depressed, 

 in other cases more cylindrical or fusiform. Anterior antennae comparatively short, 

 with the number of joints in some cases much reduced; those in male strongly 

 hinged. Posterior antennae with the outer ramus generally well developed. Oral 

 parts on the whole more fully developed than in the 4 preceding families, the 

 mandibular palp being always distinctly biramous. 1st pair of legs not prehensile, 

 but generally resembling in structure the 3 succeeding ones; inner ramus of the 

 latter well developed and 3-articulate, like the outer. Last pair of legs in some 

 cases simple, lamelliform, but more generally of normal structure, with both joints 

 well defined. Only a single ovisac present in female. 



Remarks. In this family I comprise a number of genera, which more or 

 less distinctly group themselves around the well-known genus Tachidius of Lillje- 

 borg, and which agree with those belonging to the 3 preceding families in the 

 non-prehensile nature of the 1st pair of legs, but differ materially in the much 

 fuller development of the oral parts and of the natatory legs. In addition to 



