TAPS 4! eo regs 
186 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
22 Spine moderate, springing from the middle of 
the caudal margin. . ... . . . arcuata, 190 
tt Head uncrested. 
2 Spine short or absent. 
|| Abdominal process united at the base. . gibbosa, 19f 
\||| Abdominal processes discrete. 
‘| Spine near the middle of the caudal margin. 
° Anal teeth 20 to 22. . . . . =. +. Ovata, 192 
os Anal teeth Sto lO) 7. >. 4). -obtusa,eios 
| Spine at the dorsal angle. ~ . . . alpina, 192 
22 Spine of considerable length. 
|| Spine near the middle of the caudal margin. 
‘' Ventral margin of the head convex. . hastata, 192 
“ Ventral margin of head concave. 
° Eye distant from the margin of the 
eager 
°° Eye near the margin of the head. 
x Abdominal processes united at the 
base. . . . . . . . Schoedleri, 195 
xx Abdominal processes discrete. brevispina, 193 
\||| Spine nearer the dorsalangle. . . . . pulex, 193 
** Claws of the post-abdomen without a basal comb of teeth. 
yj Antennal setze thick, first segment longer than the second. 
{ Spine near the middle of the caudal margin. ventricosa, 195 
ornata, 192 
ti Spine above the middle of the caudal margin. . caudata, 195 
t+} Antennal sete with the second segment longer than the first. 
tt; Headhelmeted:- 77). :°03. © fe te, £0 vallinagels> 
tt Head not helmeted. 
2 Abdominal processes united. 
|| Dorsal margin strongly carinate. . . . . Sarsii, 198 
\||| Dorsal margin slightly or not carinate. 
‘| First abdominal process much the longer. 
° A deep depression separating head and 
body. See veo paludicola, 198 
°° A very slight depression separating head 
and body. longispina,199; minnesotensis, 199 
“* Abdominal processes nearly equal. 
° Anal claws 12 to22. . . . . Gavifrons, 200 
°° Anal claws 7 to 23. . . . microcephala, 200 
22, Abdominal processes discrete. j 
| Abdominal processes short, equal. . . . rosea, 200 
||| First abdominal process twice as long as the second. 
" Beak not greatly produced ventrad. . aquilina, 200 
“ Beak greatly produced ventrad. . . lacustris, 201 
{it Head with a dorsal toothed crest. 
2 Crest just in front of the heart. . . . . dentata, 201 
22 Crest over the bases of the antenne. . . dentifera, 202 
II. Pigment spot absent. 
A. Head not helmeted or but slightly so. . . . . . . longiremis, 202 
B. Head helmeted. . 
