MACROTHRIX. 103 



Genus 3 — Macrothrix.* 



Macrothrix, Baird, Aim. Mag. Nat. Hist., xi, 87, 1843, and xvii, 412 ; 



Trans. Berw. Nat. Club, ii, 149. 

 Daphnia, M. Edwards, Hist. Nat. Crust,, iii, 384. 



— MiUler (?), Eutomost. 

 Lynceus, Desmarest, Cous. gen. et part. Crust,, 370. 

 MoNOCULUS, Jurine, Hist. Monoc. Geneve. 

 AcANTHOCERCUS, Sckodler, Ericlis. Arciiiv, 1840. 



Character. — Superior antennae flat, one-jointed, pen- 

 dulous from the beak. Filament from extremity of first 

 joint of anterior branch of inferior antennae much longer 

 than any of the others. Eye accompanied with a black 

 spot. 



1. Macrothrix laticornis. Tab. XV, fig. 2. 



Daphnia curvirostris (?), Muller, Eutomost., t. 13, f. 1, 2. 

 MoNocuLUS LATICORNIS, Jurine, Hist. Monoc, t. 15, f. 6. 

 Lynceus laticornis, Desmarest, Cons. gen. part. Crust., 370. 

 Macrothrix laticornis, Baird, Ann. ]\Iag. Nat. Hist., xi, 87, t. 3, 

 f. 9, 10; Trans. Berw. Nat. Club,ii, 149. 

 Acanthocerctis curvirostris (?), Sckodler, Erichs. Arcliiv, 1840. 



The shell or carapace is of an oval shape, transparent, 

 colourless, smooth, strongly ciliated on anterior margin. 



The inferior antennae or rami are strong and large 

 (t. XV, f. 2 a). The posterior branch has four setae ; three 

 from the extremity of the last articulation, and one from the 

 extremity of the second. The anterior branch has five setae, 

 four disposed as in the posterior branch, and one very long, 

 from the extremity of first articulation. Superior an- 

 tennae pendulous from the extremity of the beak, rathei' 

 broad, becoming narrower at their base, and furnished 

 with three short setae at their extremities. 



Eye large, distinctly areolar, and having an accom- 

 panying black spot near the root of the superior antennae. 



* MfiK-po^, long; and ^p'^, a hair. 



