OF DENISON UNIVERSITY. 
53 
GENUS MONOSTYLA, Ehr. 
Shell depressed, oval ; head opening large, notched before and behind. The 
foot has two short basal segments and a long terminal one ending in a small spine, 
hence appearing as though bearing one long spine. The eye is single and situ- 
ated at the base of a large ganglion. The maxtax is large and quadrate. The 
viscera are simple. 
Monostyla (quadridentata, Ehr. ?) 
Two species of Monostyla have been thus far encountered, one of ' 
which may be identical with M. quadridentata of Ehrenberg. The 
body is bell-shaped or inverted pear-shaped, the oral margin being 
produced into two sickle-shaped spines turned outward, which are dis- 
tinct from the acute margins of the shell itself. The body is com- 
posed of two segments or apparent segments, the second being small 
and conical. The terminal joint of the foot is slender and elongate, 
bearing a thorn-like spine. The ganglion is very large. The maxtax 
is also large and opens into a sack-like alimentary canal not evidently 
subdividedi The shell in this species is ornamented with granules. 
Length of lorica, .15 mm., width, .11 mm., terminal caudal joint, with 
spine, .08 mm. Found in June, in Minnesota. 
A second species is smaller, measuring from .11 to .12 mm., foot 
.04 to .08 mm., width, .11 mm. The shell is smooth and the curved 
spines are absent. 
The following species are known : — 
Monostyla lunar is ^ Ehr., M. cornuta., Ehr., M, closterocerca^ 
Schm., M. oophthalma., Schm., and M. macrognatha, Schm. 
GENUS DISTYLA, Eckstein. 
Shell ovate conical, closed behind, except for the small opening admitting the 
foot. In front, the opening is wide and guarded on either side by projecting an- 
gles. The foot is one-jointed and bears two equal, divaricated spines. The 
shell may be smooth or ornamented with raised lines and serrations. The eye is 
single and seated upon a considerable ganglion. Two species are described by 
Eckstein from Europe (jD, gissensis and D. ludwigii) and two additional ones occur 
in America. 
Distyla minnesotensis, sp. n. 
This is a large species, .25 mm. long, with a pear-shaped body of 
two segments, the first being .20 mm. long and of equal width. The 
second segment is .05 mm. long and has an oval slit behind for the in- 
sertion of the foot and permitting its free lateral motion. The claws 
