THE WATER FLEAS (CLADOCERA) 



7*5 



114(109) Head much depressed ; rostrum close to margin of valves. Anten- 

 nules slender, not enlarged near distal end. 



Macrothrix borysthenica Matile 1890. 



Dorsal margin of head evenly rounded over into that of 

 valves without sinus. Front of head recurved so that ros- 

 trum is very close to valves. Antennules with a few scat- 

 tered fine hairs; olfactory setae small, equal. Post-abdomen 

 elongated, bilobed; with numerous fine spinules and hairs 

 on both lobes. Claws small. Eye moderate; ocellus at 

 rostrum. Color transparent. Length, 9. to i.i mm. 



Albuquerque, New Mexico (Herri ck). 



FIG. 1115. Macrothrix borysthenica. (After Matile.) 



115 (198) Dorsal margin of head curved abruptly in front of eye. Antennules 

 slender Macrothrix rosea (Jurine) 1820. 



Form broadly ovate. Valves reticulated, crested, not serrate. Head large; its dorsal mar- 

 gin rounding over abruptly into anterior margin. Antennules long, slender, not enlarged near 

 apex; lateral sense-hair near base on small elevation; olfactory setae unequal. Post-abdomen 

 extended into blunt process, on which abdominal setae are borne; pre-anal part semi-elliptical, 

 with numerous spinules along convex edge and many fine hairs; anal part with several small 

 spines. Claws small, smooth. Summer eggs numerous; ephippium well-developed, with 2 eggs. 

 Antennules of $ long, curved. Post-abdomen terminating in long, fleshy projection on 

 which the vasa deferentia open. Hook of first foot serrate at tip. Color transparent to 

 yellowish or sometimes a ruddy tinge. Length, 9 ca. 0.7 mm.; $, 0.4 mm. Common 

 everywhere in marshy pools and margins of lakes. 



M. tenuicornis Kurz is a variety of this species All $ $ found in America agree with M . 

 elegans Sars. 



O.I MM. < . 



FIG. 1116. Macrothrix rosea. 



