50 
BULLETIN OF THE LABORATORIES 
make it reasonably sure that our species is really D. Tigris. It is 
quite variable in size and form. The cylindrical body is strongly 
curved ventrally. The head is distinctly set off from the body by a 
suture as represented by Eyferth but not by Eckstein. The sides of 
the neck extend into a sharp spine on either side, which, however, may 
be easily overlooked. There is a sensory cylinder which forms a third 
prominence upon the front. The foot consists of but a single evident 
segment which is quite short. The appendages assume a variety of 
appearances. Usually they seem to form a flattened triangular plate 
curved in the same plane as the body. This appearance is figured by 
Eckstein, though he describes the appendages as consisting of two pairs, 
the outer half as long as the inner, both being united at the tips into 
one plate. Eyferth says, on the other hand, that the foot bears two 
unequal, bristle-like, curved claws, but his drawing shows two equal 
claws. Our experience confirms Eyferth’s account. Like Rattulus, 
this species moves in circles or arcs of circles when lashing its tail, but 
has the power of moving in a straight line by the use of the cilia alone. 
The maxtax is nearly as drawn by Eckstein. The chief organs are 
two anchor -like indurated processes which are unlike in length and 
form. The walls of the maxtax are furnished with ring-muscles. 
The stomach is glandular and its cells contain large globules of fatty 
matter. The intestine is pear-shaped and furnished with numer- 
ous cilia. The contracting vessel is large but the lateral vessels 
are not easily seen and I can add no details. The single cervical eye 
is large and seated on a large elongate ganglion. The ovary is small 
and the egg, when present, occupies the left side of the body on its 
ventral aspect. The total length is about .20 mm. of which the body 
forms .16 mm. The longer claw measures, in large specimens, .048 
mm. and the shorter only .036 mm. Sometimes I fancied that I saw 
two lateral spines as described by Eckstein. The width of the lorica 
is about .65 mm. This species was encountered in Ohio and Minne- 
sota in all situations and seasons. 
Diurella insignis, sp. n. 
[Plate 1 V. Fig. 6. ) 
A larger species than the above is found in Minnesota. The 
length, exclusive of the claws, is from .17 to .20 mm. The claws 
are .06 mm. long, one being much longer than the other. There are 
spines in the cervical region sim.ilar to those described in in the above, 
