-J* STATE GEOLOGIST. 243 



A second variety or species has been found which differs somewhat 

 from typical mucronata, but does not appear to be nasuta of Birge. Is 

 not the latter a variety simply ? 



SCAPHOLEBEEIS AEMATA Var. ? nOV. 



Length tot -To'o cm.; much as S. mucronata in form; but the spines are 

 greatly elongated in old as well as young individuals; and in individuals 

 having winter as well as summer eggs, though the winter form seems 

 to have longer spines which are nearly equal in some cases to the 

 hight. Antennae are short and transparent. The head is separated 

 from the body by a marked depression; but is curved forward so that 

 the beak lies generally between the valves. The antennules are of 

 medium size. Nowhere reticulate ( ?) nor tuberculate. The shell is 

 marked by impressed lines, especially anteriorly and below. The lower 

 margin is straight and beaded anteriorly, but toward the base of the 

 mucro are several long bristles which stop abruptly and are followed by 

 a few very weak hairs. The post-abdomen has three teeth at the base 

 of the claws, which are smooth. 



This variety is much like S. nasuta of Birge, perhaps, but differs per- 

 ceptably in several points. Most conspicuous are the greatly elongated 

 spines and the short antennae. This variety is about as large as 

 mucronata but less than nasuta. 



BOSMINIDuE. 



Grenus bosmina. 



First antennae many -jointed; intestine straight. Sole genus of the 

 family, and one which Kurz characterizes as " one of the most difficult 

 of the genera of Cladocera." 



There are three species known in the United States, two of which 

 are found from the Eastern States to the Mississippi and westward, and 

 are 'identical with European forms. The third may not prove distinct 



BOSMINA LOlfGIKOSTRIS. 



(Plate X, fig. 2.) 



Differs from the following in having the terminal claws not toothed, 

 and from B. striata in the shorter antennae and reticulate shell. 



