ENTOMOSTKACA OF MINNESOTA. 233 



the middle, and are serrated. The antenniiles are long and slender, 

 but do not reach to the end of the rostrum. They have each a flagel- 

 lum and sense hairs. The antennae are small and have eight (f^x) 

 setse and two (j^%) spines. The labrum resembles that of ^4. leuco- 

 cephalus, but is slightly prolonged at the apex. The intestine, ccecum 

 and color resemble those of Acroperus. There is a trace of a keel pres- 

 ent on the back." 



The specimens seen in Minnesota resemble this species very nearly, 

 apparently, but there are some differences. The terminal claw of the 

 post-abdomen has an increasing series of spines to the middle; there 

 seems to be no lateral row of scales beside the anal teeth; the abdo- 

 men is rather broad at the base and narrows toward the end. The 

 shell is not square behind. The lower margin has a few long hairs 

 anteriorly which are followed by a series of teeth, and in the concave 

 part a somewhat longer set to a point just before the lower curved 

 angle. 



The pigment fleck is nearly or quite as large as the eye. The an- 

 tennule is shorter than the beak (which is almost as in Pleuroxus 

 hastafus), and has a flagellum about midway; at its base it is narrowed 

 and inserted on a prominence. 



The embryo still in the brood sac has a more elongate form and 

 hexagonal reticulations upon the shell, while the antennules were 

 longer than the very long beak, and the pigment fleck was smaller 

 than the eye. Length of female 0.52 mm. The color is darker, and 

 the striae more numerous, than in A. latissima. 



From a private letter we learn that this form is now regarded as 

 simply a variety. 



Series B. — This section includes Leydigia, Graptoleheris, DunhevhUa {^Crepidocer- 

 cus), Lynceus, Alona, Alonella, Pleuroxus, Phrixura, Chydorus, Anchisfropus, MonospUus. 



GENUS LEYDIGIA Kurz. 



In this genus, both the known species of which are found in 

 America, the posterior part of the shell and body is emphasized at 

 the expense of the anterior. The curved posterior margin is equal to 

 the greatest height of the shell. The head and anterior part of the 

 body are of the form characteristic of Alona: indeed, the whole body 

 is in plan like Alo7ia, but in the back part the organs are all enlarged. 

 The general form of the body and abdomen recalls Ihjoenjptm: the 

 post abdomen, in particular, is very like that genus. The last two 

 pairs of feet are much enlarged. The shell is usually irregularly 

 marked with longitudinal strite; the lower margin is covered with 

 long spine-like setae. The post-abdomen is armed with several sets of 



