31 



peels moderately strong, with the 1st basal joint generally subdivided in the 

 middle, and provided anteriorly with a small rounded lobe carrying 2 plumose 

 setae; digitiform lobe issuing from the end of this joint anteriorly comparatively 

 small, with none of the setse unguiform. Posterior maxillipeds much more slender, 

 and composed of 4 well-defined joints. Natatory legs with both rami generally 

 3-articulate. though in some cases, by an imperfect separation of the 2 outer joints, 

 one or other of them, or all, may be only biarticulate ; inner ramus of 4th pair with 

 2 apical spines. Last pair of legs very small and generally not extended laterally, 

 being composed of 2 joints, the proximal of which in some cases may be coalesced 

 with the corresponding segment, distal joint not expanded, and carrying a slender 

 apical seta and a short lateral spine. Seminal receptacle in female of compara- 

 tively simple structure, being generally transversely oval in shape. 



Remarks. This genus is here taken in a much more restricted sense 

 than done by other authors. Owing to the great number of species referred to 

 this genus, it has long appeared very desirable to group them according to their 

 mutual relationship, in order to get a clear survey on them. A such grouping 

 of the European species has indeed been effected by Dr. Schmeil in his very 

 valuable work on the fresh water Copepoda of Germany. I think, however that 

 we may be justified to take a further step, and to subdivide the old genus Cyclops 

 into a number of nearly-allied genera, each being designated by a particular 

 name. In the present work I have attempted to do so, distinguishing 5 different 

 genera, the name Cyclops being restricted to one of them, which comprises the 

 greater bulk of the hitherto known species. In this genus I have included 4 of 

 the 8 groups of Cyclopses distinguished by Dr. Schmeil, having not found sufficient 

 reason for a generic separation of these groups; the 4 other genera answer to 

 as many groups distinguished by Dr. Schmeil. 



In the restriction here adopted, the present genus is, among other things, 

 characterised by the well defined and angular epimeral parts of the segments 

 composing the anterior division of the body, giving to the sides of that division 

 a more or less jagged appearance. Of the structural details, it is especially the 

 rudimentary last pair of legs which exhibits a very characteristic appearance, 

 conspicuously differing from that in any of the other 4 genera. 



A considerable number of species referable to the present genus 

 will be described in the sequel, some of them being, however, so closely 

 allied, that their specific distinctness has not generally been recognised. They 

 all, like the species of the 4 succeeding genera, are exclusive inhabitants of 

 fresh water. 



