Dr. W. Baird on British Entomostraca. 87 



into two separate valves. Leach's characters of the genus are 

 equally incorrect: "two eyes; four antennaj, branched*." 

 We have stated above the incorrectness of these characters. 

 Straus's characters are equally infelicitous : " Rami with tvro 

 branches, divided into a much greater number of articulations 

 than in the other genera of this family ; primitive stalk very- 

 short." He gives as the type of this genus the spJieericus of 

 Miiller, but these characters do not agree with those belong- 

 ing to that species, as the rami are each possessed of only 

 three articulations. In the brachyurus of Miiller the rami have 

 numerous articulations, but from MliUcr's figure they appear 

 to be four in number instead of two. Milne Edwards is the 

 last writer who has characterized this genus. His characters 

 for the different genera belonging to the family Daphnidiens 

 he adopts from Straus, taking them from the number of 

 branches and the number of joints to each branch of the 

 rami. In Lynceus he says, " at least four joints to each of the 

 branches t :" this is decidedly incoiTcct in all the species we 

 have met with. The subgenus Chydoriis of Leach, as esta- 

 blished by him in ' Sup. Encyc. Britan.,' 1816, for the recep- 

 tion of L. spharicus of Miiller, is equally unhappily character- 

 ized : " two eyes ; antennae two, in shape of threads." These 

 characters are decidedly incorrect, the rami (antennje) being 

 branched and jointed in that species as well as the others. 



We propose ybr the present reforming this genus as fol- 

 lows : — 



Fam. DAPHNID^. 

 Genus Lynceus. 



" Rami two, for the most part very short, branched ; each 

 branch 3-jointed. Eye single, accompanied with a black spot 

 in front of it. Feet, five pairs. Intestine convoluted. Tail 

 jointed." 



1st Subgenus. Macrothrix J. " Anterior branch of ra- 

 mus having a very long seta or filament springing from root 

 of second articulation. Antennas pendulous from extremity 

 of beak." 



1st Sp. Macrothrlx laticornis. PL II. f. 9, 10. 

 Syn. Daphnia curvirostris ? Miiller, Ent. t. 13. f. 1, 2. — Monoculus 

 laticornis, Jurine, 1. 15. f. 6. — Lynceus laticornis, Desmarest, p. 37o. 

 — Daphnia laticornis ? M. Edwards, iii. p. 373. 



* The species brachyurus of Miiller is the type of Leach's genus ; but as 

 this anomalous-looking species is one I have nev'er met with, though Leach 

 mentions it as common, I have not been able to ascertain its precise cha- 

 racters. It must form a new genus. 



f " Au moins quatre articles a chacune des ces branches," iii. p. 374. 



X From i^xK^oi long, and 6(n^ a hair. 



