Harring and Myers—The Rotifers of Wisconsin . 647 
The body is elongate, fusiform, and slender; its greatest width, 
at mid-length, is one fourth of the total length. The integument 
is very flexible, but the outline is quite constant. The entire 
body is very transparent. 
The head and neck segments are of nearly 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 and very slightly in width for one half its length, 
and then tapers gently to the tail, which is very broad and in¬ 
distinctly three-lobed. The foot is fairly long, two-jointed, and 
slightly tapering; its length is about one fourth of the total 
length. The toes are straight and slender, cylindrical for two 
thirds of their length, and conical at the tips; their length is one 
tenth of the total length. 
The dorsal and lateral antennae are small setigerous papillae 
in the normal positions. 
The corona is frontal and consists of a marginal wreath of 
cilia, much reduced dorsally and passing in a curve to a lateral, 
auricle-like area of strongly developed cilia; the ventral arcs 
meet immediately below the mouth. The buccal field is faintly 
ciliate. 
The mastax is a specialized form of the virgate type and very 
closely resembles the structure of the mastax in Sphyrias lofuana 
(Rousselet). 1 The rami are roughly triangular and symmetri¬ 
cal; at the base they are expanded into broad, somewhat de- 
curved lamellar alulae, and near mid-length they are bent rather 
abruptly at a nearly right angle toward the dorsal side. The in¬ 
ner edges are strongly reinforced and enclose an elongate lyrate 
opening, which is widest near the middle of the ventral portion; 
from this point to the tips the rami are armed with numerous, very 
close-set, pointed teeth, increasing in size toward the dorsal ends. 
The fulcrum is long and straight; it is formed of two plates 
joined at the dorsal edges, so that the cross-section is Y-shaped; 
the Y is narrow at the base and spreads gradually, so that the 
posterior two thirds of the fulcrum is right-angled in section. The 
posterior end is dissected into fine fibrillae, imbedded in the mus¬ 
cles of the piston. The unci have only a single, strong tooth; at 
the base there is a minute lamella with two or three striae, repre- 
1 Harring-, Proc. U. S. Natl. Mus. 46 (1913) : 400, PI. 37, figs. 4-8. 
