Earring and Myers—The Rotifers of Wisconsin. 645 
erable variation with the contractions of the animal. The entire 
body is very transparent and indistinctly fluted longitudinal. 
The head and neck segments are of about equal length and 
width, approximately three fourths of the greatest width of the 
body; the transverse folds separating head and neck as well as 
neck and abdomen are not very distinct. The abdomen increases 
gradually in width for one half its length, and then tapers gently 
to the base of the foot, which is as broad as the posterior end 
of the abdomen. The tail is very indistinct and visible only in a 
lateral view. The foot is very short and broad, without any 
joint. The toes are peculiar; the base is a very broad, flattened, 
bulbous enlargement, passing abruptly into the slender, slightly 
decurved and incurved posterior section. It is possible that the 
basal bulb really is a second foot joint, but there is no external 
indication of this. 
The dorsal and lateral antennae are small setigerous papillae 
in the normal positions. 
The corona is very slightly oblique and consists of a simple 
marginal wreath of cilia, very short dorsally and somewhat longer 
laterally, closed on the ventral side immediately behind the mouth. 
The buccal field is covered with short, close-set cilia; the apical 
plate is unciliated. 
The mastax is of a type intermediate between the normal Notom- 
mata and the Enteroplea type; while still retaining the pump¬ 
ing action of the virgate mastax, it has become adapted to 
attack upon living prey. The rami appear triangular in ven¬ 
tral view; at a point near mid-length they are bent at a right 
angle toward the dorsal side and provided with two fairly large 
teeth in each ramus. There is a small, lozenge-shaped opening 
in front of the angle, and an elongate, narrow opening dorsally. 
The rami are intricately ribbed and webbed to resist deformation 
through muscular action. The fulcrum is straight and tapers 
gradually to the posterior end, where it is slightly expanded for 
attachment of the muscles of the piston. The unci have only 
a single tooth; a very thin and quite narrow lamella attached 
to the dorsal side represents the normal additional teeth. To the 
tip of the left tooth are attached two minute pre-uncial teeth, and 
to the right a single similar tooth. The central portion of the 
manubrium is nearly straight and tapers gradually to the poste¬ 
rior end; the dorsal and ventral extensions are thin lamellae of 
moderate size. A slender rod, pointed at both ends and bent 
