110 BRITISH COPEPODA. 



Cyclops serrulatus, Claus. Das Genus Cyclops, p. 36, figs. 1 — 3 

 (1857). 



— — Sars. Oversigt Ferskvandscopepoder, p. 45 



(1863). 



— — Claus. Die frei-lebenden Copepoden, p. 101, 



t. i, figs. 1,2; t. iv, fig. 12 ; t. xi, fig. 3 (1863). 



— — Fric. Die Krustenthiere Bokmens, p. 222, 



fig. 18 (1871). 



— — Uljanin. Reise in Turkestan (Crustacea), 



p. 34, t. viii, figs. 1—8 (1875). 



Body slender and elongated ; anterior antennae 

 slender, 12- jointed, reaching to the middle of the 

 third cephalothoracic segment, tapering gradually 

 towards the apex, the last three joints being very 

 long and slender. Fifth pair of feet 1 -jointed, 

 bearing two slender setae and a ciliated lancet-shaped 

 spine. Abdomen slender and elongated ; caudal seg- 

 ments (fig. 6) slender, from four to six times as long 

 as broad, and bordered externally with a comb-like 

 row of minute spines. Tail setae beset with five short 

 cilia ; outermost and innermost seta? short, the others 

 of moderate length, the innermost and longest of 

 the two being not very much longer than the abdo- 

 men. Length ^th °f an mcn ('98 mm.). The 

 colour is very variable, apparently depending much 

 upon the character of the food supply ; it may be 

 olive-green, dark brownish-red, or almost colourless. 



G. serrulatus is an extremely common species, 

 more abundant, indeed, than any other of the genus, 

 occurring in all kinds of localities from the highest 

 mountain tarns down to pools on the very verge 

 of the sea, and seeming to delight as much in the 

 muddy ditch as in the clear waters of the lake. A 



