STATE GEOLOGIST. 71 



The body is broad and very narrow, the lower outline is angled 

 and nearly unarmed; the pigment fleck and eye are small and ap- 

 proximated; antennules very long and curved backward and out- 

 ward; abdomen short, ciliate below; claws short, ciliated. This 

 female had a full complement of eggs but the antennae resemble 

 those of a male. This is unusually interesting and should be redis- 

 covered and studied; for there seems to be some affinity between 

 this species and Bosmina, and it is probable that it requires to be 

 distinguished generically from Macrothrix. 



II. GrENUS Lathonuba, Lilljeborg. 



The form is oval ; the head is curved more than in Macrothrix 

 and the shell is more obtuse behind, sinuate below where it is beset 

 with short spines anteriorly; first antennae long, straight; second 

 antennae with five setae on each ramus; only four pairs of feet ap- 

 parent; abdomen short, prolonged upward to the insertion of the 

 caudal stylets; male similar but smaller. 



Sp 1. Liathonura rectirostris, 0. F. Mueller. 



(Plate D.) 



Daphnia rectirostris, o. f. murller. 



PasitJiea rectirostris, koch, Deutschland's Krust., etc. 



Daphnia brachyura,z\DDXC's,Syn. Crust, prussicorum. LTEVi>r, Die Branch, d. 



Danziger Gejrend. 

 Daphtiia mystacina, fischer, St. Petersb. Branchiop, 

 Latlwnur a rectirostris, lilljeborg, De Crust, ex ord. trib. 

 Pasithea rectrirostris , leydig, Naturg. d. Daph. 

 Lathonura rectirostris, noRUAN a.nd brady, Mouogr. Brit. Eut. ; p. e. mueller, 



Danmark's Ciadocera, 

 Lathonura spinosa, schoedler, Brauchiop. d. Umg. v. Berlin. 

 Pasithea rectirostris, GRUKEPx. and weishiaxn, Ueber einige neue od. unvolllc. ge- 



kaunte Dapli. 

 Lathonura rectirostris, birge, Xotes on Ciadocera. herrick, Notes on Minnesota 

 Ciadocera. 



The only species of the genus is distributed probably over the 

 entire northern temperate zone. It has been found in America at 

 Cambridge, Mass., and in the vicinity of Minneapolis, at both of 

 which places it is very rare. 



The form is a rather quadrangular oval, the head being strongly 

 arched to the beak which is much farther posterior than in Macro- 

 thrix, in this respect resembling the Daphnidae; the eye occupies 

 the center of the lower part of the head mar2:in, and is of moderate 

 size; the pigment fleck is near the base of the antennules and well 

 removed from the eye; the antennae are straight and long, with a 



