214 GEOL. AND NAT. HIST, SURVEY OF MINNESOTA. 
Macrothrix serricanudata Daday. 
Shell rounded, punctate, transparent, obtusely angled caudad. 
Caudal part of dorsal margin serrate, ventral margin nearly straight, 
sparsely ciliate cephalad. Antennules long, subcylindrical, attenuate 
at the end, slightly curved, armed with minute sete. Post-abdomen 
rounded at the end, sinuous above the anus, serrate with strong teeth. 
Length 0.9 to 1.0 mm. This species is near to our own M. pauper. 
*Macrothrix rosea Jurine. 
PLATES LIV, Fies. 1-3; LVI, Fiaes. 5-7, 11, 13. 
Monoculus roseus—Jurine. 
Lynceus roseus— Desmarest. 
Daphnia rosea—M. Edwards, Jurrell. 
Echinisca rosea—Lievin. 
The body is sub-oval, terminating behind in an acute angle; the 
lower margin is less conspicuously spined than the last or the following; 
the antenne are but slightly dilated at the end and nearly straight. 
The longest seta of the antenne is longer than in the last, reaching 
beyond the tips of the terminal sete; abdomen more slender, sinuate 
in front, beset with short hairs. 
Length 0.6 mm., male 0.8mm. The male has small claws on the end 
of the post-abdomen, and the antennules are curved and elongated. 
In a later publication Birge finds small claws on the post-abdomen 
of the male which resemble that of Bosmina. On the posterior side of 
the apex of the antennules of the male is a cluster of five or six long 
sense hairs peculiar to this species. 
*Macrothrix tenuicornis Kurz. 
PLateEs LIV, Fies. 5-8; LVI, Fias. 1-3, 12, 20. 
(See Notes on Cladocera of Minnesota, p. 245.) 
The body is oval, produced posteriorly in a sharp point; the ab- 
domen is strongly arched, while the upper outline of the head is a 
regular curve or slightly extended in front of the eye; the antennules 
are long, nearly straight and a very little narrowed toward the end, 
just in front of which is a series of short teeth; there is no lateral 
spine, but a strong terminal one in addition to the sensory filaments; 
the pigment spot is large, the eye small and the lobus opticus well 
separated from the ganglion; the antennz have a very powerful basal 
joint; the elongated seta is very stout and densely spiny, with a tooth 
at its flexure; two of the terminal sets are spiny, for the basal half; 
the valves are beset with very long spines in sets of three each, all 
having different positions; the abdomen is nearly as in M. rosea, but 
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