j Earring and Myers—The Rotifers of Wisconsin. 595 
The mastax must probably be considered as belonging to the 
virgate type, but the pumping action has been completely lost. 
The trophi are strongly asymmetric and very robust. The fulcrum 
is a short and very broad plate without any posterior enlargement. 
The rami are lyrate in ventral view and are bent nearly at a right 
angle at the extreme anterior point; the dorsal branch is rather 
short. The right ramus has on its inner edge a very large lamellar 
and semicircular projection, the margin of which is marked with 
radial striations and very faintly denticulate; at the apex of the 
ramus there are two broad and very blunt teeth. The left ramus 
is strongly concave on the inner ventral edge, which is relatively 
broad and marked with numerous very narrow transverse striae, 
giving it the appearance of being denticulate; the large apical 
teeth of the right ramus are lacking. The alulae are fairly 
prominent. The ventral tooth of the left uncus is extremely large, 
rather short and strongly clubbed at the point; this is followed by 
three minute, comblike, rudimentary teeth and a fairly large, 
rather blunt dorsal tooth at the junction of the dorsal rib and 
a curved diagonal rib crossing the basal plate from the base of 
the large ventral tooth. The right uncus has a large ventral 
tooth, blunt and clubbed at the tip; from its base radiate two 
similar teeth, nearly as large; on the dorsal margin is a small 
tooth which, like the opposing tooth on the left uncus, is formed 
by the junction of the dorsal rib and a diagonal rib starting 
from the base of the ventral tooth. The manubria are unequally 
developed, the right being only three fourths of the length of 
the left and its posterior end nearly straight, while the left 
manubrium curves strongly inward and toward the dorsal side. 
The anterior ends of both manubria are broadly expanded, the 
thin lamina on the dorsal side continuing for three fourths of 
the entire length. Below the posterior edge of the dorsal branch 
of each ramus there is a short, robust, curved rod imbedded in 
the walls of the mastax; its ventral end rests on the inner sur¬ 
face of the ramus and the dorsal ends meet below the tips of the 
rami; in the normal virgate, pumping mastax this rod without 
doubt aids in the support of the walls of the mastax during the 
pumping action, but it is not evident what its function, if any, 
may be in this case. 
The oesophagus is long and slender; gastric glands, stomach- 
intestine, and ovary are normal. The bladder is formed by a 
