ENTOMOSTRACA OF MINNESOTA. 197 
this species are the well crested head, which in young as well as 
sometimes older specimens has a median hyaline ridge, the with- 
drawal of the eye from the margin and the very long spine. It reseim- 
bles D. galeata in earlier stages. It is very much like D. levis or, in 
other words, is in the group of D. hyalina. This form has only been 
found in autumn, September to November, Lake St. Croix and Rich- 
field in Hennepin county. 
[*Daphnia thorata Forbes. ] 
Forkes 793. 
‘‘This species belongs to the hyalina group, and may possibly be 
entitled only to varietal rank. The distinctness and constancy of its 
characters, however, in collections made by us in Flathead and Swan 
lakes in western Montana, and the number of minor points in which 
it differs from hyalina, as most recently described, lead me to distin- 
guish it as a specific form. 
‘*Tt is oval in outline; the long and slender posterior spine is 
placed at or a trifle above the middle; the length of the head is about 
a third that of the valves of the shell excluding the spine, and there is 
no trace of dorsal emargination between head and body. ‘The head is 
narrowed toward the base and elongated forward in a way to give it 
the outline of a bell jar with a flaring base. Its front is broadly and 
‘regularly rounded, its ventral margin usually conspicuously concave 
and closely like the dorsal, although occasionally the head is straight 
or convex beneath. The posterior margin is either straight or slightly 
concave, and the beak stands free from the front margin of the valves, 
and by its extension downward not only covers the antenne but 
reaches clearly beyond the tips of the sensory hairs. The eye is of 
medium size, placed far back of the front of the head and equidistant 
from the tip of the beak and the dorsal junction of the head and body. 
The pigment speck is of moderate size, placed directly behind the 
eye, and much farther from it than from the posterior margin of the 
head. The antenne are moderately stout, entirely smooth except for 
inconspicuous transverse rows of minute appressed hairs upon both 
peduncle and rami, and a row of short, tooth-like spinules at the dis- 
tal end of each segment. The swimming hairs are rather slender, the 
second joint commonly decidedly shorter than the first. Fornices 
slight, arising above and a little behind the eye and terminating 
directly behind the antennz, above the bases of which they project 
but slightly. The lower margin of each valve is set with the usual 
spinules almost to the beak, and the dorsal margin is similarly armed 
for a distance in front of the spine about equal to half the length of 
