Harring Myers—Rotifer Fauna of Wisconsin — 11. 463 
The corona is an obliquely frontal disc with long marginal cilia 
and two lateral tufts of densely set long cilia, especially adapted 
to swimming; the apical plate is enclosed by the marginal ciliation; 
the buccal field is sparsely ciliated. The mouth is slightly below 
the center of the corona and the lips occasionally project as a 
^‘beak.’’ 
The mastax is virgate; the fulcrum is long and straight, nearly 
always slightly expanded at the posterior end to provide a greater 
surface for the attachment of the muscles of the piston; the rami 
are imperfectly developed, the uncus having only a single, slender 
tooth and the manubrium usually rodshaped, with or without a 
terminal crutch; the piston is a large, powerful muscle attached to 
the fulcrum and filling the entire cavity of the mastax. 
The retrocerebral organ is absent in nearly all the species and 
rudimentary when present, being limited to a small sac with par¬ 
tially atrophied duct, which does not reach the surface of the 
corona. The eyespot may be cervical, frontal (single or double) 
or absent. 
Type of the genus.—Cephalodella catellina (Muller )=06rcarm 
catellina Muller. 
The definition of this genus, which includes all the species of 
Diaschiza Gosse, as revised by Dixon-Nuttall and Freeman, has 
been broadened sufficiently to admit some evidently closely related 
species. We have based it on the peculiar form of the body, a 
head segment separated from the abdomen by a slight constric¬ 
tion, no distinct separation between the abdomen and foot, corona 
slightly oblique with mouth near the center, and the specialized 
type of the virgate mastax, which varies only in minute details 
throughout the genus as here constituted. We do not consider 
the divided lorica as a generic character; in many species it is only 
a polite fiction. Neither can the small tuft of setae at the base 
of the toes be accepted as such; it is so difficult to find that we 
have made no use of it; although the genus includes a great many 
species, they are readily distinguished by easily ascertainable 
differences. 
The ‘ ‘ beak ’ ’ must be observed in the living animal; in preserved 
material the lips nearly always project somewhat. We have not 
figured the trophi of all the species included, as the differences 
are slight, but enough have been given to show the range of varia¬ 
tion within the genus. 
