ENTOMOSTEACA OF MINNESOTA. 243 



It would appear that the lateral line of scales upon the post-abdo- 

 men may be absent. There is often, if not always, a cluster of fine 

 spinules above the spine on the otherwise smooth claw of the post- 

 abdomen. 



Alona guttata Sars. 



Norman and Brady '67 (Lynceus gattatus); Kurz '74 (parviila and tuberculata) ; 

 Hellich '77 (anglica, and guttata); Matile '90. 



A small species of sub quadrangular form. The beak is very 

 short; the eye small, but larger than the minute pigment fleck. The 

 shell is short, with a rounded posterior angle and marked by hexag- 

 onal or rectangular meshes running about parallel with the lower 

 margin. Tne post-abdomen is of moderate size, rounded at the apex, 

 with a series of stout teeth behind; the terminal claw has a minute 

 basal spine. P. E. Mueller, in Danmark's Cladocera, confused this 

 with A. intermcdta, which he described under this. The post-abdo- 

 men in that species is larger, less rounded behind, and armed with 

 clusters of spines instead of teeth. The length is about 0.3 mm. in 

 both. In males the hook is small and the anal spines are absent. 



^^^'■^Alona ])arvnla Kurz is said to have the body sub quadrangular, 

 arched above; ventral margin straight, rounded behind. Shell marked 

 by longitudinal, feeble and irregular lines. The post-abdomen is nar- 

 rower toward the end, with eight or more teeth; the row of scales is 

 absent; at the end it is sharply truncate and incised; the claws have 

 short basal spines. Hardly to be distinguished from the next. 



'^'■^AJona parvula var. tuhercnJdta Kurz (Alona tuberculata Kurz) de- 

 scribed by Kurz in 1874, and more at length by Lutz under a difierent 

 name {Alona verrucosa) in 1878, appears to be simply a tuberculate 

 variety of the above. Observations upon the American representa- 

 tives of the two forms indicate a close relationship between them. The 

 shell is covered with rows of tubercles (or depressions?) which vary in 

 number greatly. 



"I do not know how to distinguish ^^ Alona </?rtcmi/s Birge (Plate 

 LXIII, Figs. 2, 3 and 8) certainly from A. imrvula. It, however, seems 

 to have the lower angle of the post-abdomen less squarely truncate and 

 the incision less obvious. Birge says that the abdomen is rounded. 

 I have found specimens which apparently belong here, with the post- 

 abdomen rather sharply angled and deeply incised; there were about 

 fourteen teeth with a row of hairs in front. The form is hardly to be 

 distinguished from another variety which has a shorter post-abdomen, 

 rounded below, and with only about seven or eight teeth and with a 

 smooth shell. This form passes directly into a tuberculate variety, 

 liaving the post-abdomen similar but the shell covered with numerous 

 16 



