34 TWELFTH ANKDAL REPORT. 



Sp. 1 . Moina rectirostris, Mueller. 

 (Plate A. Figs. 2, 5, 8, 10, 11.) 



A. Var. vera. 



Daphnia realiroslrU, O F- MOKLLER, Latreille, BOSC, Desmarest,SCHRA.Nk,Letdio. 



Monoculas rcciiroslris, GMBLIN, FaBRICIUS, MANDEL; JURINE. 



Pasilhea rectirostris, KoCH. 



Moina rectiroflris, Baikd, WeismanN, Kurz, Birge. 



li. Vur. bracliintiis. 



Moiioculus brachialus. JORINE. 



Dapania brrichiala, DESMARE3T, EDWARDS, Leydig. 



Moina brac'iialn, Baird, WeISMANN. 



C Both varieties. 



Moina brachiala. P. E. MUHLLER. LilljeboRg, 



The only tangible difference between the two forms thus united 

 is the fact that M. rectirostris produces but a single winter ovum 

 and hence has a one-chambered ephippium, while M. brachiata has 

 a two-chambered ephippium. 



The head is separated Irom the thorax by a marked depression ; there 

 is a deep depression above the eye; the margins of the shell have few 

 bristles. The post-abdomen, which extends far beyond the edge of the 

 valves, bears about eleven hairy spines on either side, the lower 

 spine being two-cleft at the end; the base of the claws bears a 

 comb of small teeth, and the posterior margins are bristled. The 

 ephippium is oval; and the single cavity in M. rectirostris has 

 its longer axis horizontal, while the two cavities of M. brachiata are 

 vertical. The depression above the eye is deeper in the males, in 

 which sex also the antennae are longer and bent at the middle. 

 Tiie seminal bodies are stellate. Length 1, 2 mm. The ^orm is 

 .-subject to the greatest variation due to the varying number of sum- 

 mer eggs. Birge finds this species abundant. I have found both 

 this and the following species in various parts of the Mississippi 

 ^yalley from Mobile to the upper river region. 



Sp. 2.— Moina paracloxa, "Weismaun. 



(Plate A. Figs. 1, 3, 6, 7, 9.) 



The species differs in a few very insignificant points from the 

 previous one. The head is short and nearly evenly convex 

 above, with no deep depression above the eye; teeth of terminal 

 claws reduced to bristles which are only a little longer than the 

 series extending down the claw as in the above species; the first 



l"Gruber and Weistnann, ueber einige neue oder unvollkmmen gekannte Daphniden 

 Freiburg, 1877 



