324 History of British Entomostraca. 
or less 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 instructa ; 
ovario externo unico. 
Synonimes, fyc 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 Cseruleus. M. rubens, Fabricius, Entom. System. 1792. 
Cyclops Caeruleus, 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. 1^ long. Body of six articulations ; first largest. 
Tail of five ; the last sending off" two lobes, each of which gives ori- 
gin to five 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 ofremi. 
