OF DENISON UNIVERSITY. 
49 
GENUS POLYARTHRA, Ehr. 
A single species has so far been encountered and I am able, with 
the works at hand, to discover no reason to doubt its identity with P. 
platyptera of Ehrenberg. 
When swimming freely this animal seems to consist of two quad- 
rilateral segments, the first, or head segment being considerable shorter 
than wide in outline, while the body is a third longer than wide. The 
trochal ciliation is slight. Two sensory organs are conspicuous upon 
the front of the head and the eye occupies the middle of the first 
segment near its posterior margin. The maxtax is very large and the 
stomach is short, with a tubular intestine. There are two prominences 
on either side of the body near the front, each bearing three lanceolate 
spines. The egg is very large and is perhaps half as bulky as the 
whole body. The contractile vessel is small and little could be seen 
of the lateral vessels. The length is .10 mm. ; width, .08 mm, ; setae, 
.088 mm. long. This species seems rare and was found among plauts 
in standing water during June and July of 1884 and 1885 near Min- 
neapolis. 
The group of genera termed Macrodactylea or Longiseta includes 
such animals as have a more or less elongate and frequently cylindrical 
body, often strongly curved, and possess the following characters. 
The cuticle is considerably indurated; the terminal segment of the foot 
is long ; there is usually a lack of symmetry exhibited by the claws or 
maxtax; and the cilia are sparse upon the trochal disc. 
The following genera are at present included in the family : 
Scaridium, Mojtura, Furadaria^ Disteinma^ AIonocerca,Mastigo- 
cerca, Diurella^ Heterognathus ^ Rattulus. 
GENUS DIURELLA, Bory de St. V. 
The body is more or less perfectly cylindrical, and curved either ventrally or 
dorsally. The claws are rather long and frequently seem united, and are curved 
ventrally. The eye is cervical and single. There is a sensory tube upon the 
upper (dorsal) part of the disc. Three species are described, although doubt ex- 
ists as to the specific value of one of these; they are D. tigris, Ehr., D. Rattulus^ 
Eyferth, and D. stylata, Eyferth, to which a species is added below under the name 
D. insignis. The common species in America is 
Diurella TIGRIS, {EJiv. ) Bory. 
The descriptions and figures of European authors vary remarkably 
in this instance, but from them ah we are able to gather sufficient tO 
