360 KEY. A. M. NOEMAN AND MR. 



Family. MACEOTHRICIDJE. 



Anterior antennae one-jointed, articulated to the extremity of 

 the rostrum, and movahle in both sexes ; furnished with auditory 

 cilia at their extremity, these cilia being usually large and ten- 

 taculiform. Posterior antennae two-branched, branches sub-equal, 

 slender, and cylindrical; one branch three, the other four-jointed. 

 Feet five pairs, with sometimes the rudiment of a sixth pair, 

 separated by a nearly equal interval from each other, the last 

 provided with a branchial lamella, which is generally large and 

 extended longitudinally. Intestine either simple or convoluted. 



Genus. MACROTHRIX, Baird. 



Carapace ovate, more or less produced centrally behind ; ven- 

 tral margin serrulated and ciliated, cilia simple. Anterior an- 

 tennae large, conspicuous, one-jointed, cylindrical, or strap-shaped, 

 attached to the extremity of the rostrum. Posterior antennae 

 having the four-jointed ramus furnished with four, and the three- 

 jointed with five setae, the lowermost seta of the latter geniculate 

 like the other setae, but very long, and differing from them in 

 structure. A black eye-spot situated between the eye and the 

 end of the rostrum. Abdomen very deep, edged with hair-like 

 spines, and terminating in two very small simple claws. Intes- 

 tinal canal perfectly simple. Inhabitants of lakes and other clear 

 pieces of water. 



1. Macrothrix laticornis, {Jurine.) PI. XXIII, figs. 4, 5. 



1820. Monocukis laticornis, Jurine. Histoire des Monocles, p. 

 151. PI. XY, figs. 6, 7. 



1850. Macrothrix laticornis, Baird. British Entomostraca, p. 



103. PI. XV, fig. 2. 



1851. Macrothrix curvirostris, S. Fischer. Mem. presentes a 



l'Academie Imp. des Sciences de St. Petersbourg, par 

 divers Savants. Yol. YI, p. 184. PI. VII, figs. 7-10. 



1853. Macrothrix laticornis, Liiljeborg. De Crust, ex Ord. 

 tribus. Clad. Ost. et Copep., p. 50. PI. Ill, figs. 8, 9. 



