* 
ti 
ENTOMOSTRACA OF MINNESOTA. 215 
the posterior margin has a series of long sharp teeth; the mandibles 
are nearly completely exposed by the arched anterior margin of the 
valves. 
The labrum, in this species, is an odd link between that of the 
Daphnide and Lynceide. The basal segment is greatly enlarged and is 
sub-triangular in outline, with a movable lip attached to the inner 
free face; the typical daphnoid structure is preserved, but the enlarged 
salient angle of the basal portion shows how the transition to the great 
triangular labrum of Alona, etc., is made. In young specimens the 
head is proportionately larger, the antennules are broader at the tip, , 
and the dorsal outline is less convex; the marginal spines of the valves 
are also proportionally larger, as are the appendages of the first and 
last pairs of feet. This is one of the largest species of the genus, 0.75 
mm. being the length. This is very close to M. rosea but seems 
distinct. 
This form is quite commom about Minneapolis, Minn., but is not 
yet noted elsewhere in America. 
*Macrothrix pauper Herrick. 
PLATE LVI, Fie. 4. 
This species is described from a single specimen from Lake Minne- 
tonka, and I can add nothing to the very meager notice given then. 
(Herrick ’82.) 
The body is broad and very narrow, the lower outline is angled 
and nearly unarmed; the pigment fleck and eye are small and approxi- 
mated; antennules very long and curved backward and outward; ab- 
domen short, ciliate below; claws short, ciliated. This: female had a 
full complement of eggs but the antennze resemble those of a male. 
This is unusually interesting and should be rediscovered 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. 
GENUS LATHONURA 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 antenne long, straight; second antennz 
with five setze on each ramus; only four pairs of feet apparent; ab- 
domen short, prolonged upward to the insertion of the caudal stylet; 
male similar but smaller. 
a 
