ENTOMOSTRACA OF MINNESOTA. 239 
more nearly represent our present knowledge of the genus than that of 
the previous edition. Unfortunately the key must be based on the 
statements of other authors, and in this genus it is rare to find com- 
plete agreement between the published descriptions. The best thing 
a student can do is to disregard much of the synonomy and make an 
exhaustive study of aspecies from a large number of individuals in 
one locality and then cautiously extend the range of work to include 
adjacent stations. 
KEY TO THE GENUS ALONA. 
I. Macula cerebri much larger than the eye... Sanguinea, 239; moniezi, 240 
II. Macula cerebii about as largeas the eye. quadrangularis, 240; (affinis, 240 
oblonga, 240;) lepida, 242... . . . (Seealso intermedia, 244) 
III. Macula cerebri smaller than the eye. 
A. Post-abdomen narrowed toward the end, at least not broadly rounded. 
a. A single series of anal spines. 
* Strice oblique to the axis ofthe shell. . . . . lacustris, 242 
** Striz parallel to the axis of the shell. 
{ Abdomen very long, with long anal spines, (One form of) 
tenuicaudis, 242 
tt Abdomen not very long. . . . . guttata, 243 
b. A lateral as well as an anal series of naats cahlonminal spines, setze 
or scales. 
* Post-abdomen long and slender. (Usual form of) tenuicaudis, 242 
** Post-abdomen of ordinary form. 
{+ Aval spines two. Row of sete in addition. . dentata, 244 
tf Anal spines represented by trausverse clusters of bristles. 
intermedia, 244 
{tt Anal spines large, nearly equal... . . . . pulehra, 245 
ttt? Lower anal spines larger... . . . . . . porrecta, 246 
B. Post-abdomen broadly rounded below. 
a. Analspinesinasingleseries. . . . . . . . Stagnalis, 246 
b. A double series of anal spines. 
* Strize of shell close, fine and oblique. . . . . elegans, 247 
** Strize of shell distant. 
{ Strie oblique. . . . . . angulata, 247 
+{Striz parallel to the initia dindlas axis anuie shell. coronata, 247 
(Not noticed inthe key. . . . . . . . costata, 245; barroisi, 248) 
* Alona sanguinea P. E. Mueller. 
PEATE: LCi Fire 20: 
Body nearly rectangular; ventral margin nearly straight, with short 
sete; posterior angle rounded, unarmed. Beak short; pigment fleck 
much larger than the eye. Post-abdomen large, the end truncate, 
broadened; posterior margin rounded, with a series of spines and a 
