102 BRITISH COPEPODA. 



the furca ; third about half as long again as the 

 second ; innermost half as long as the third. Length 

 of the female x^-th of an inch (2 '55 mm.), that of the 

 male about one third less. Colour dusky brown or 

 approaching black, or bluish ; ovisacs dark. 



This is one of the most widely distributed and 

 commonest of the genus, occurring not unfrequently 

 in ponds, lakes, and ditches. The characters of the 

 first and second antennas, together with those of the 

 ovisacs, suffice to distinguish it almost at a glance. 



I have had no opportunity of seeing Koch's figures 

 of 0. signatus, but Professor G. 0. Sars states that 

 they are quite characteristic and belong, undoubtedly, 

 to the species now under consideration. 



2. Cyclops tenuicornis, Glaus. PI. XVIII, figs. 1 — 10. 



Cyclc>2)s tenuicomis, Claus. Das Genus Cyclops, t. iii, figs. 1 — 11 ; 

 Die frei-lebenden Copepoden, p. 99, t. i, 

 fig. 3 ; t. ii, fig. 17 ; t. iv, fig. 5 (1857). 



— — Sars. Oversigt af de indenlandske Fersk- 



vandscopepoder, p. 33 (1863). 



— — Uljanin. Reise in Turkestan (Crustacea), 



p. 30, t. ix, fig. 12, 13 (1875). 



— — Fric. Die Krustenthiere Bohmens, p. 219, 



fig. 12 (1871). 



— quadricornis albidus, Jurine. Hist, des Monocles, p. 44, 



t. ii, figs. 10, 11 (1820). 



— — var. b, Baird. Brit. Entom., p. 202, pi. xxiv, 



fig. 4 (1850). 



Body somewhat narrower than in the preceding 

 species. Anterior antennae (fig. 2) nearly as long as 



