174 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
Ceriodaphnia cornuta Sars. 
Sars ’85. 
This interesting species furnishes further evidence of the close re- 
lation between Ceriodaphnia and Scapholeberis by the possession of a 
frontal spine or ‘“‘horn.’?’ Head much depressed, with frontal part 
slightly dilated. A process arises directly cephalad of the eye, an- 
other forming a beak. Carapace broadly oval, tumid, with a bifid 
caudal projection from the upper angle. Whole shell distinetly retic- 
ulate with polygonal markings. Antennules short, fusiform, lateral 
seta near the middle. Two distinct abdominal processes. Anal spines 
about eight. Claw without basal teeth. Length 0.6mm. The form 
resembles OC. quadrangula. The fornices are acute. 
GENUS SCAPHOLEBERIS. 
The genus Scapholeberis stands rather closely related to Ceriodaph- 
nia, from which it is at once distinguished by the angled or spined 
lower posterior angle of the shell, The head is rather clumsy, and the 
continuation of the fornices runs toward the apex of the incurved beak, 
which commonly lies within the valves of the shell. The lower ante- 
rior angle has a prominence and there is a basin-shaped area inclosing 
the base of the antennie, part of which lies on the shell and part on 
the head. This area is more strongly lined or reticulated than the 
rest of the shell. The lower margin is straight and terminates, in 
most forms, in a long scythe-shaped spine which is directed backward. 
The shell itself is usually indistinctly reticulate or unmarked, and 
commonly is deep colored. The post-abdomen is very like Ceriodaph- 
nia or more as in Simocephalus; the anal spines are few and the older 
Specimens have more than the young; the place at which additional 
spines are to appear is marked by prominences. The eye is of mod- 
erate size, the pigment fleck rather small and the antennules short 
and hidden by the beak. The antennz are of small size and generally 
dark colored. The ephippium contains but one egg; the males do not 
have altered antennze or feet. The sexual periods fall in early sum- 
mer and in autumn, according to Weismann; the males appear but 
sparingly. The species S. mucronata is very abundant everywhere, 
while the others are less frequently seen. 
* Scapholeberis mucronata Mueller. 
PLATES XLIII, Fias. 4-7; XLV, Fia. 5. 
Dophnia mucronata—Mueller, Lievin, Lil)jeborg, Fischer, Leydig, Baird, Herrick. 
This well-known species with rather short spines below is found 
