200 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
from the body by a marked depression. The spine of the shell springs 
from the upper angle or is quite wanting. The post-abdomen is of 
moderate size, Somewhat narrowed toward the end. The claws are 
smooth, the anal spines nearly equal, straight, about fourteen in 
number. The abdominal processes are not coalesced or but slightly 
so. Length 1.50 mm. to 2.0 mm. The species was collected sparingly 
in a large gathering of D. pulex from a small lake in early spring. 
‘‘The size and conformation of the abdominal processes are very 
variable and the long and very slender spine is frequently absent.’’ 
The antennules are very short. Males unknown. 
Daphnia microcephala Sars. 
A small transparent form, head only half as deep as the shell, 
slightly concave ventrally and ending in a short blunt beak. Shell 
elongate oval with a slender somewhat curved spine from the middle 
of the caudal margin. Abdominal processes nearly equal and united 
at the base. Analspinesseven. Claws without teeth. Length 0.75 mm. 
This is also a species requiring farther study. 
Daphnia cavifrons Sars. 
A reddish species with the head separated from the body by a 
depression, depressed, ventral border excavated, beak large. Shell 
ventricose with a short spine from near the upper angle. Abdominal 
processes nearly equal and united at the base. Anal teeth 12. Claw 
without teeth. Length 1.5 mm. 
I am not sure of this and the preceding. 
* Daphnia rosea Sars. 
Of moderate size, reddish in color, and resembling D. longispina. 
Head depressed and not separated by a depression from the thorax, 
somewhat excavated in the ventral margin, beak blunt. Shell oval, 
spine long, springing from above the middle and directed obliquely 
dorsad. The two abdominal processes thick, equal, discrete. Anal 
spines 12 to 14. Claw without teeth. Length 1.9 mm. 
The American form identified with this species is more like D. 
longispina. 
Daphnia aquilina Sars. 
A species of medium size, transparent. Head depressed, protuber- 
ant at the eye, excavated behind it, the beak lying in the same plane 
as the frontal projection and strongly curved caudad. LHye large. 
Shell oval, slightly separate from the head. Spine above the middle 
