8 A ItEVISION OF THE BKITISH SPECIES OF 



3. Cyclops strenuus, Fischer (PI. II., figs. 1-4). 



1820. Monoculus quadricornis rubens, Jurine (3), p. 1, pi. I.; 



pi. II., fig. 1-9. 

 1841. Cyclops pictus, Koch (4), H. 21, pi. I. 

 1851. ,, strenuus, Fischer(8),p.419,pl.IX., figs.12-21. 



1853. ,, quadricomis, Lilljeborg (9), p. 150, pi. XIV., 



figs. 5, 6; pi. XV., figs. 1-12; 

 pi. XXVI., fig. 19. 

 1857. ,, brevicaudatus, Claus (13), p. 34, pi. II., fig. 12. 

 1863. ,, „ Lubbock (19), p. 200. 



1863. „ Clausii, Lubbock (19), pi. XXXI., figs. 12-14. 

 1863. ,, strenuus, G. 0. Sars (20), p. 27. 



1872. ,, brevicaudatus, Fric (24), p. 221, fig. 15. 

 1878. ,, strenuus, Brady (32), p. 104, pi. XIX., figs.1-7. 



1885. „ ,, Daday (44), p. 216. 



1886. ,, ,, Vosseler (46a), p. 195, pi. IV., 



figs. 18-22. 



Though not nearly so common a species as the foregoing, 

 C. strenuus seems to be pretty generally distributed, having 

 been found in Russia by Fischer, in Norway by G. 0. Sars, in 

 Germany (Claus), Hungary (Fric), Holland (Hoek). It has not, 

 however, as yet been noticed in America. 



I have notes of its occurrence in the following British locali- 

 ties: Belsay andPlessey, Northumberland; Seaton Marsh, county 

 Durham; Staithes, Yorkshire; Llanfairfechan, North Wales; 

 (G.S.B.) ; Loch Leven, Kinross {Mr. T. Scott) ; Lambton Park, 

 county Durham ; Loch Hutton and Carlingwark Loch, Kirkcud- 

 brightshire ; Grasmere and Lough Neagh {Rev. Br. Norman). 



4. Cyclops abyssorum, G. 0. Sars (PI. III.). 

 1863. Cyclops abyssorum, G. 0. Sars (20), p. 29. 



Female. — Body subtruncate in front, gradually tapering back- 

 wards, first segment forming at least half the length of the 

 cephalothorax ; the second, third, and fourth segments are not 

 greatly produced laterally, but are abruptly narrowed in front 

 and the posterior margins form acute angles laterally ; the fifth 

 segment is short, narrow, and much constricted in front: the 

 abdomen is more than half as long as the cephalothorax, its 

 first segment not greatly narrower than the last thoracic, wider 

 in front and equal in length to the following three segments; 



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