176 GEOL. AND NAT. HIST. RUEYEY OF MINNESOTA. 



*Scapliolel)eris aurita Fischer. 



Daphnia aurita — Fischer. 

 Scaphohberis nasuta — Birge. 



Form mucli as in the last, head shorter, "prolonged into a rather 

 sharp beak, at whose apex the continuations of the fornices unite. 

 The beak does not project downward as in S. nmcronata, but backward, 

 and in its natural position lies between the valves." The usual reticu- 

 lated and lined areas are present and the balance of the shell is covered 

 with "small pointed projections." "The antennules are much larger 

 than in S. ynucronata, though they do not project beyond the rostrum." 

 The pigment fleck is long and large; the post-abdomen is much as in 

 the preceding species; the terminal claws have several fine teeth. 

 The males have the opening of the vas deferens close behind the 

 terminal claws; raucro short and blunt, length 1.0 mm. This species 

 is very near the next, but differs in several particulars. It forms the 

 transition to the next, which is the extreme of the genus in a direction 

 converse to that pursued by the 8. armata. 



* Scapholeberis aug^ulata Herrick. 



Plates XLII, Figs. 9, 9a; XLV, Figs. 7, 7a. 



Herrick '83. 



Form as in the above, but comparatively larger; valves quadran- 

 gular, anterior margin strongly arched; head short, only slightly con- 

 cave below the eyes; the beak is as in S. nasuta, but seems to be directed 

 more nearly directly downward than in that species. The antennules 

 are long and resemble those of jSimocephalus. The pigment fleck is 

 square and rather large; the antennae are of the usual size. The re- 

 ticulated areas are as in the other species. The post-abdomen is more 

 as in Daphnia, not so squarely truncate and with five to seven large 

 teeth; the first foot has one elongated jointed seta; the posterior angle 

 of the shell has no spine, at most there is a somewhat prominent acute 

 angle, the inner shell layer is armed at this point with some elongated 

 teeth as in the corresponding situation in Sbnocephalus. On the whole, 

 there is a similarity to that genus in this as well as in the previous 

 species. S. nasuta has a short spine and elongated pigment fleck, the 

 present species has a squarish but rather large fleck and no spine; the 

 post- abdomen has a greater number of spines than any other species. 

 South of Tennessee river, in Alabama and Mississippi. 



The species of this genus are predominatingly American, four out 

 five being found in the United States; the fifth, moreover, is more 

 often regarded a variety of one of the others; in fact, the absence of 



