Harring and Myers—The Rotifers of Wisconsin. 569 
The mastax is virgate, with strongly asymmetric trophi, and, 
in proportion to the size of the animal, larger than in any other 
species belonging to this genus. The fulcrum is very long, stout, 
and slightly tapering, the curvature gradually increasing towards 
the posterior end. Beginning at a point near mid-length there 
is on the ventral edge a Y-shaped groove of gradually increasing 
width; its sides are formed by two thin, corrugated lamellae, 
which provide increased surface for the attachment of the muscles 
of the piston and give it a Y-shaped cross section. The anterior 
end of the fulcrum has a blunt, angular projection at the base 
of the rami; immediately behind this the right ramus has a broad, 
lamellar tooth with coarsely denticulate margin curving obliquely 
towards the left. Opposite this tooth the left ramus is deeply ex¬ 
cavate. The alulae are very large and somewhat asymmetric; 
their external angles are a considerable distance below the base of 
the rami. The unci are roughly square, and each has three teeth, 
united by a plate-like web; only the ventral tooth in each uncus 
is developed. The inner margins of the unci are thickened and 
marked with irregular, longitudinal striae. The left tooth is 
extremely large, broad, blunt, and clubbed at the point; the right 
tooth is a little smaller but of the same general form; on the ven¬ 
tral edge there is near the point a spirally twisted projection, 
corrugated like the inner margin of the unci, and opposing the 
left tooth. The second and third teeth in each uncus are rudimen¬ 
tary and do not project beyond the inner margin. The manubria 
are very long and broad; a wide, double-curved, thin lamella ex¬ 
tends nearly to the posterior end on the dorsal margin. Be¬ 
low the posterior edge of the rami there is a curved rod imbedded 
in the walls of the mastax; the ventral end rests on the inner 
surface of the ramus, and the dorsal ends meet below the tips 
of the rami. 
The oesophagus is very long and slender. Gastric glands and 
stomach-intestine are normal. The ovary is elongate and broadly 
ribbon-shaped. The bladder is formed by an expansion of the 
cloaca. The foot glands are long, slender, and slightly club- 
shaped. 
The retrocerebral sac is very long, pyriform, clear, and vacuo¬ 
late. The subcerebral glands are small and somewhat variable in 
size; the dorsal and lateral views show the two extremes; a few 
bacteroids are scattered through the posterior portion of the 
