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 CeHodoplinia and Scaplwleheris 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. Caraj^ace broadly oval, tumid, with a bifid 

 caudal projection from the upper angle. Whole shell distinctly 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 0.6 mm. The form 

 resembles G. quadrangula. The foruices 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 antenme, 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 Geriodaph- 

 nia or more as in Simocejihalus; 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 antennteare of small size and generally 

 dark colored. The ephippium contains but one egg; the males do not 

 have altered antennae or feet. The sexual periods fall in early sum- 

 mer and in autumn, according to Weismann; the males appear but 

 sparingly. The species *S'. mncronata is very abundant everywhere, 

 while the others are less frequently seen. 



* Scapholeberis mucrouata Mueller. 

 Plates XLIII, Figs. 4-7; XLV, Fig. 5. 

 DapJmia mucronata — Mueller, LieYin, Lilljeborg, Fischer, Leydig, Baiid, Herrick. 

 This well-known species with rather short spines below is found 



