1046 Wisconsin Academy of Sciences, Arts, and Letters. 
The rostrum is not acute. The antennules are slender hut do 
not reach the end of the rostrum; the olfactory setae are equal. 
The valves are not inflated in antero-ventral region. They 
have markings concentric with ventral and posterior margins; 
one such being usually visible. In most specimens the valves 
are otherwise unmarked. In one specimen, however, are vis¬ 
ible longitudinal striations like those of Leydigia, and in an¬ 
other (from South America) can he seen reticulations like 
those sometimes seen in Alona. The entire ventral margin 
hears rather long, thick-set setae. The labrum has a rounded 
angle behind. The post-abdomen is very long, slender, nar¬ 
rowed toward apex. It bears about 16 marginal denticles; 
all of them long, except those nearest the anus; and the apex 
of the post-abdomen bears two which are far larger than any 
others. The last and largest one is serrate on its concave 
margin. Next anterior to these come three denticles, which 
are somewhat smaller than those proximal to them. From 
this point the series gradually diminishes in size toward the 
anus. Lateral fascicles of very fine spinules are present. The 
terminal claw is notably long, and rather straight. Its basal 
part is thicker for about one-third of the length of the claw, 
and the single long basal spine is inserted at this point. Da- 
day’s figure (’05, PI. XV, fig. 13) shows that the basal part 
is denticulated, but no such structure can be found in my 
specimens, though it would be expected. The first foot has 
no specially developed hook or claw. The eye is small, larger 
than the ocellus, which is nearer the eye than the apex of 
rostrum. 
Color yellow-brown. Length of female 0.54-0.62 mm. 
Male unknown. 
Some dozen specimens of this species were found by me in 
collections made among water hyacinths in Lake Charles, La., 
in October, 1903. I have also found exactly similar speci¬ 
mens in collections from Demerara, South America, made by 
Mr. E. T. Owen in 1901. It is co-specific with a Paraguayan 
form described by Daday (’05, p. 178) as belonging to Sars’ 
species A. tenuicaudis, and which Daday assigns to Euryalona. 
I believe that the specific identification is incorrect. At any 
