Harring and Myers—The Rotifers of Wisconsin. 597 
foot is very short and appears to have only a single joint. The 
toes are very short, conical, and slightly decurved; the extreme 
tips are somewhat abruptly curved inward and upward. At the 
base of the toes there is a very small, blunt knob-like projection 
on the posterior margin of the terminal foot joint; the length 
of the toes is about one twentieth of the total length. 
The dorsal and lateral antennae are minute setigerous papillae 
in the normal positions. 
The corona has two strongly ciliated areas corresponding to 
the auricles of other species, but not evertile. Close to the dorsal 
margin there are two small papillae, near the openings of the 
ducts of the retrocerebral sac. The buccal field is evenly ciliated 
and projects strongly in the region around the mouth, giving the 
corona in lateral view a decidedly angular appearance; the mouth 
is situated immediately above the most prominent part of the 
corona. 
The mast ax is apparently a highly modified form of the virgate 
type; the pumping action has been completely lost, and the robust 
and strongly asymmetric trophi have become adapted to prehen¬ 
sion. They can be thrust out through the mouth quite as ef¬ 
fectively as in the forcipate type of mastax. The fulcrum is 
very short and lamellar and tapers from the base to less than 
half the with at the posterior end. The rami are deeply bifur¬ 
cate and very dissimilar in form. The right ramus has near the 
base a large, rounded, ventral projection, and behind this a 
roughly parallel-sided ventral branch, obtusely pointed at the tip; 
the inner margin is thickened and marked with numerous very 
narrow transverse striae, giving it the appearance of being den¬ 
ticulate ; the striae are continued as a broad border on the ventral 
side. The dorsal branch is approximately triangular and has a 
fairly prominent tooth on its inner edge, just above the bottom 
of the deep transverse groove separating it from the ventral 
branch. The left ramus has a knob-like or tooth-like, slightly 
recurved ventral projection near the base; it is, like the right 
ramus, divided by a deep, transverse groove into a ventral and 
a dorsal branch. The ventral branch is fairly broad and lamellar ; 
on the anterior, obliquely truncate margin are two prominent 
triangular teeth; the dorsal branch has two relatively long, sharp 
teeth on the inner margin and a long, tapering, curved projection 
from its anterior end towards the dorsal side of the mastax; this 
projection is totally lacking on the right ramus. The right alula 
