34 TWELFTH ANNUAL REPORT. 



Sp. 1, Moina rectirostris, Mueller. 

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



A. Var. vera. 



Daphnia rectirostris, O. F. MOELLER, LA.TBEILLE, BOSC, DESMAREST,SCHRANK,LETDia. 



Monoculas rectirostris, GmELTN, FabriCIUS, MaNUEL, JURINE. 



Pasithea rectirostris, KoCH. 



Moina rectiroitris, BA.I8D, WEI3MA.NN, KURz, BlRGE. 



/?. Var. brachiatus. 



Monoculus brachiatus. JDRINE. 



Dapania brichiata, DBSMA.REST, EDWA8D3, LetdIG 



Moina brachiata, Baird, Weismann. 



•C. Both varieties. 



Moina brachiata. P. E. MUELLER. 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 from 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. 

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

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

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

 ithis and the following species in various parts of the Mississippi 

 Talley from Mobile to the upper river region. 



Sp 2.— Moina paradoxa, 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 Weismann, ueber einige neue oder unvollkmmen gekannte Daphniden 

 Freiburg, 1877 



