324 History of British Entomostraca. 



or Jess deep ; external ovaries not so much at a right angle with tail 

 as preceding. 



2. Cyclops Castor. Plate X. Fig. 1 — Specific Character. — Antennis longio- 



ribus ; cauda bifurcata ; furca utraque setis quinque plumosis instructs ; 



ovario externo unico. 

 Synonimes, Sfc — Dioptomus Castor, J. O. Westwood, Lardner's Cabinet 



Cyclopaedia (ined.) 

 Cyclops Castor, Desmarest, Consid. gen. sur les Crustaces, p. 363. 

 Monoculus Castor, Jurine, Hist, des Monoc. pp. 50-73, plates 4, 5, 6. 1820. 



Figures beautiful. 

 Cyclops lacinulatus, Ramdohr, Beyt. zur Naturg. pp. 7-9, tab. ii. fig. 4-12. 



1805. 

 Monoculus Caeruleus. — M. rubens, Fabricius, Entom. System. 1792. 

 Cyclops Cseruleus, Mutter, p. 102, tab. xv. fig. 1-9. — C rubens, Mutter, p. 



104, tab. xvi. fig. 1-3- 

 C. lacinulatus, Mutter, p. 105, tab. xvi. fig. 4-6. 1785. Figures tolerable. 

 Baker, Microscope made easy, p. 93, pi. 9, fig. 2, 1743. — Figures copied from 



the Phil. Trans. 

 Philosophical Transactions, No. 288, fig. 6 of accompanying plate. 1703. 

 — Very bad figure. 



Habitat Ponds and slowly-running water, as at Dunglass Pond, Yetholm 



Loch, &c. &c. in Scotland ; New River, London. Not so common as preced- 

 ing species. 



Description. — 11 long. Body of six articulations ; first largest. 

 Tail of five ; the last sending oif two lobes, each of which gives ori- 

 gin to live plumose setae. Eye large, of a fine ruby colour. Anten- 

 nae large and strong, of about twenty-six articulations ; each segment 

 furnished with one or more setae ; last one terminated by five une- 

 qually long ones. In the male, the right antenna alone has the 

 swelling and hinge-joint which characterize the sex. Antennules 

 (Fig. 2) bifid ; two branches of unequal length, arising from a com- 

 mon stalk. The shorter of the two can be carried backwards or for- 

 wards at pleasure of animal, and is composed of three articulations, 

 the first of which is short, and inserted into common foot-stalk ; the 

 second is furnished on its edge with a dozen of small dentations, 

 from which arise as many hairs ; and the third is provided at extre- 

 mity with three long hairs. * The longer branch is also composed 

 of three articulations ; the first articulated with body of animal ; the 

 third terminates in several long filaments, which have an articula- 

 tion in the middle of the length, adding much to their suppleness.t 

 Internal mandibles (Fig. 3) resemble somewhat those of preceding 

 species, but have the " barbillons" much larger and bifid, while the 



* This part of the antennule is what Muller calls the palpi, 



f This portion is what Muller describes under the name of remi. 



