Harring and Myers—The Rotifers of Wisconsin. 643 
their combined length is one fourth of the total length, and the 
anterior width is almost equal to the greatest width of the body. 
The abdomen is slightly narrower anteriorly than at mid-length; 
from this point it tapers gradually to the rudimentary tail. The 
foot is rather long and tapers gradually to the toes; there is no con¬ 
striction at its junction with the abdomen, and it has no apparent 
joints. The toes are short, about one twentieth of the total 
length, slender and tapering, with slightly blunted points. 
The dorsal antenna is unusually far back on the anterior por¬ 
tion of the body; the lateral antennae are in the normal position; 
all are small, setigerous pits. 
The corona is frontal and consists of a marginal wreath of 
cilia, interrupted dorsally and passing in a curve to the lateral 
angles, where it joins an inner circle starting below the dorsal 
gap; from the angles the corona continues as a single band, 
closed ventrally and passing immediately below the mouth. The 
inner circle has a median dorsal tuft of long cilia. The buccal 
field is very faintly ciliate. 
The mastax is of a modified virgate form, in which the pump¬ 
ing action is of secondary importance and an adaptation to the 
seizure of prey has taken place. The rami are broad and roughly 
triangular; there is only a trace of asymmetry. Near mid-length 
they are bent at a right angle and have a single, well developed 
tooth in each ramus. There is a small, lozenge-shaped ventral 
opening between the rami; the inner edges of the upper half are 
finely striate. The supporting framework of the mastax consists 
of rather slender, round rods of intricate form. The fulcrum 
is fairly long and slightly tapering toward the posterior end, 
where it passes abruptly into a quadrant-shaped expansion, some¬ 
what flattened at the tip and with a roughened surface for the 
attachment of the muscles of the piston. The unci are reduced to 
a single, rather slender tooth with three minute pre-uncial teeth 
on the left and two on the right side; at the base of the uncus 
there is a diagonal supporting piece of complicated form, with 
one end connected to the manubrium and the other to the tooth. 
The manubrium is fairly slender, its posterior end curving slightly 
toward the ventral side; anteriorly there is a large, rounded ven¬ 
tral lobe and a triangular dorsal lobe curving inwards. A slen¬ 
der, slightly curved rod, resting with its ventral end on the in¬ 
ner surface of the rami, is imbedded in the walls of the mastax 
and aids in their support during the pumping operation. The 
