59 



distance from the end, exhibits a very conspicuous semilunar incision. Posterior 

 antennae likewise unusually slender, with the terminal joint long and narrow. 

 Anterior maxillipeds with the posterior edge of the basal part distinctly crenulated. 

 Posterior pair of maxillipeds of the usual structure. Natatory legs comparatively 

 slender, spines of outer ramus rather coarse, the distal outer spine of the terminal 

 joint apparently issuing from the tip itself, outer edge of the joints very finely 

 spinulose; terminal joint of inner ramus in all pairs unusually prolonged, being 

 fully as long as the other 2 joints combined, setae of inner edge in the 3 posterior 

 pairs rather far from the apex and some of them reduced in size; apical spines of 

 this ramus in 4th pair almost equal-sized; connecting plate of same pair produced 

 behind, on each side, to an acute projection. Last pair of legs with the distal joint 

 rather narrow, both seise very slender and elongated, the inner one somewhat remote 

 from the tip. Ovisacs of moderate size and somewhat diverging. Seminal receptacle 

 exhibiting the form characteristic of the genus, anterior lobes somewhat exserted at 

 the ends, posterior part extending almost to the end of the genital segment. 



Colour generally pale yellow, with a more or less distinct bluish 

 green tinge. 



Length of adult female 1.00 1.30 mm. 



Remarks. I have no doubt that the C. obsoletus of Koch is in reality this 

 species. The figure he gives is rather characteristic, and cannot properly be 

 adduced to any other species. As the specific name proposed by Koch is much 

 older than that given to the species by Glaus, it must be retained for the present 

 form. The C. Seotirfieldi of Brady is the same species, and according to Dr. 

 Schmeil, C. simplex Poggenpol also is to be regarded as a synonym. 



Occurrence. This is one of our commonest Cyclopids, occurring very 

 abundantly both in small ponds and ditches and in larger lakes. In the latter 

 it lives as a true limnetic form, being found everywhere near the surface of the 

 water together with other limnetic animals. 



Distribution. Throughout Europe, central and northern parts of Asia, 

 Ceylon, central and southern parts of Africa, North America, Brazil, Patagonia, 

 Australia. The cosmopolitan distribution of this species is very remarkable. 



34. Mesocyclops oithonoides, G. 0. Sars. 



(PL XXXVI). 



Cyclops oithonoides, G. O. Sars. 1. c. p. 32. 

 Syn : Cyclops hyalinus, Rehberg. 



Specific Characters. Female. Body very slender, with the anterior division 

 narrow oblong in outline, greatest width not nearly attaining half the length and 



