150 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
GENUS LATONA Straus. 
PLATE XXXYV, Fig. 8. 
Body elongate, broad; head large and square, appendaged below 
with triangular laminze; fornices present. Antennules rather large. 
The larger ramus of the antenne is two-jointed and has an expanded 
process at the base. The lower posterior angle of the shell has a pe- 
culiar diverging set of sete. The shell is often ornamented with 
numerous flecks of bright color. There is a copulatory apparatus in 
the male. 
* Latona setifera Mueller, 
Is the only species, and is not yet recognized in Minnesota, but was 
found by Professor Birge in Lake Michigan. 
Professor Birge mentions ‘‘one peculiarity not mentioned by any 
European writer. There is a thick coat of short hairs on the head, 
body and antenn. ‘These hairs are 0.02 mm. or less in length, are — 
close set and give the outline a velvety appearance when seen by 
transmitted light. It lives in clear water among weeds.”’ 
GENUS LATONOPSIS Sars. 1888. 
Allied to Zatona. Impression between head and thorax slight or 
absent. Labrum devoid of plate like expansion. Antennule with a 
long, plumose, straight or curved flagellum, articulated to the basal 
part. Antenna with simple rami, the superior ramus bi-articulate, 
the inferior tri-articulate, as in Daphnella. Heart concave dorsally, 
truncate anteriorly, the aorta arising on the ventral side. Shell gland 
with three long branches. Male with simple copulatory organ, and 
hook on first leg. Antennule long, slightly curved, armed with fine 
teeth, resembling in general the antennule of Sida but having a 
median projection near the base. 
* Latonopsis occidentalis Birge. 
PLATE XXXVIII. 
Birge ’91. 
Anterior outline of head forming a nearly straight line from the 
antennules to the eye, where it passes by an abrupt curve into the 
nearly straight continuous margin of the shell, which, however, be- 
comes convex in old females. The ventral margin is continued into 
the labrum and lacks the leaf-like appendages of Latona. Smal] 
bilobed fornices are present. The ventral margin of the shell is 
evenly rounded, passing without marked projection into the straight 
caudal margin. The edge of the shell is fringed with long plumose 
