b 
ENTOMOSTRACA 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 guttatus); Kurz ’74 (parvula 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. The 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. intermedia, 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 parvula 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. 
** Alona parvula var. tuberculata Karz (Alona tuberculata Kurz) de- 
seribed by Kurz in 1874, and more at length by Lutz under a different 
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. 
‘‘T do not know how to distinguish *Alona glacialis Birge (Plate 
LXIII, Figs. 2,3 and 8) certainly from A. parvula. 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, 
having the post-abdomen similar but the shell covered with numerous 
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