Harring & Myers—Rotifer Fauna of Wisconsin — II. 439 
small and enclosed by the marginal wreath; the buccal field is 
evenly ciliated and the mouth is at or near the ventral margin. 
The mastax is intermediate between the malleate and the vir- 
gate types; the fulcrum may be either short or long; the rami are 
symmetrical, large and triangular, with a well developed basal 
apophysis; the unci have about eight slender teeth, clubbed at the 
tips; the manubria are long. No epipharynx is present; the piston 
is partly or wholly attached to the fulcrum. 
The retrocerebral organ is rudimentary or absent; the eyespot, 
when present, is cervical. 
Type of the genus.—Proalinopsis caudatus (Collins) —Notom- 
mata caudata Collins. 
PROALINOPSIS STAURHS Harring and Myers, new species. 
Plate XX, figures 5-9. 
The body is fairly slender and spindle-shaped; its greatest width 
is about one fourth of the entire length. The integument is very 
flexible and the outline constantly changing in response to the 
contractions of the animal. The entire body is as hyaline as 
P. caudatus. 
The head and abdomen are separated by a deep constriction. 
The head segment is somewhat longer than wide and convex ante¬ 
riorly; its width is about two thirds of the greatest width of the 
body. The abdomen is spindle-shaped and widest near the middle; 
from there it tapers gradually to the tail, a small, knoblike pajpilla 
bearing a stiff spine, one fifth as long as the body. The foot is 
stout and fairly long; it has two joints, the terminal somewhat 
longer than the basal. The toes are rather stout at the base and 
end in very slender, acute points; their length is a little less than 
one fifth of the total length. 
The dorsal antenna is a large, knoblike elevation in the normal 
position; it has a funnel-shaped central depression with a small 
tuft of sensory setae. The lateral antennae have not been observed. 
The corona is an elongate oval area covering the oblique anterior 
surface of the head and terminating a short distance below the 
mouth on the ventral side. The marginal cilia are rather short, 
except on two lateral, auricle-like areas, which are provided with 
long and powerful cilia for swimming. The unciliated apical plate 
is small; the buccal field is evenly ciliated. 
