no. 1758. ON MARINE COPEPODA IND CLADOCERA.—SHARPE. 417 



Family IDY1ID.E. 

 Genus 1DYA Philippi, 1843. 



IDYA FURCATA (Baird). 



Cyclops fin-cat us Baird, Mag. Zool. and Bot., vol. 9, 1837, figs. 2G-28. 

 Canthocamptus furcatus Baird, British Entomostraca, L850, p. 210, figs. 1-6. 

 Tisbe furcat us Claus, Die Freilebenden Copepoden, L863, p. I Id, figs. 1 -12. 

 Idyafurcata Brady, Copepoda of the British Islands, vol. 2, L880, p. L72, figs. 

 1 LI. (!.(). Sars, Crustacea of Norway, vol. 5, L903, p. 88, 11 figs. 



Length. — Female, average, 1 mm.; male, 0.65 mm. Maximum 

 length of deep-water variety, 1.5 nun. 



Charactt rs. — Body of female whitish in color and more oi less trans- 

 versely banded with clear crimson; ovarial tubes commonly of a clear 



dark color. 



Caudal rami scarcely as long as the anal seg- 

 ment. Fifth pair of legs of the female with the 

 inner expansion of the proximal joint broadly 

 rounded and armed with three seta', the middle 

 one rather slender, the other two very small; 

 distal segment sublinear, with five slender seta 1 , 

 of which three issue from the tip and two from 

 the outer edge close to the end. 



Remarks. — Perhaps the commonest and most 

 widely distributed of all the Harpacticoida. 

 While it is most commonly to be found with 

 littoral foiin>, yet a larger pelagic form is to be 

 met with at greater depths on decaying algae. 

 ture, swimming about with great speed, now and then affixing itself t<> 

 fronds of the alga' or to the walls of the vessel in which it is being 

 observed" (Sars). 



Occurri nee. — Collected with a birge net amongst float ing alga- and eel 

 grass at Little Harbor. Woods Hole, July. Water about 10 feel deep 

 at high tide, sandy bottom. Also from Eel Pond, Woods I Iole, August. 



Distribution. — Arctic Ocean, widely distributed; British seas; Kat- 

 tegat ; coast of France (Canu); Mediterranean and \Uh] seas (A. Scott); 

 New Zealand (Brady); Pacific at Chatham Islands (Sars); Franz 

 Josef Land (Scott); Narragansett Bay, Rhode Island (Williams). 



Family THALESTRIDjE. 



Genus THALESTRIS Claus, 1863. 



THALESTRIS GIBBA (Krbyer). 



l/urpacticus gibba Kroyer, Gaimard's Voyage en Scandinavie, 1845, pi. 13, 



figs. 2, a-p. 

 riinlcstris gibba, G. O. Sars, Crustacea of Norway, vol. 5, L903, p. L05, pi. 61, 



12 figs. 



Length. — Female, 1 .5 mm.; male slightly smaller. 

 Characters. — Color of body, except dorsal face of the cephalic 

 segment, dark bluish gray to almost black. Posterior edges of 

 Proc.N.M.vol.38— 10 27 



Fig. 9.— Idya furcata. a, 



FIFTH FOOT OF MALE; 6, 

 FIFTH FOOT OF FEMALE. 



A vei v active crea- 



