310 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Internal organs. — The internal organs offer nothing of especial interest. The trophi differ 
from those of D. porcellus Gosse in being straighter and more slender and in not showing in side 
view the long transverse piece which makes the left manubrium so conspicuously “ crutch-shaped ” 
in the latter species. (Compare the trophi as shown in figs. 12 and 21.) 
Measurements. — Length of body, 0.09 to 0.12 mm.; of toes, 0.03 to 0.04 mm.; total, 0.12 to 
0.16 mm. 
History. — This species was figured by Weber (1898, pi. 20, figs. 2-4) as Coelopus porcellus 
Gosse ( Diurella porcellus Gosse). Weber’s description confuses the two species; thus, the two 
teeth at the anterior edge, mentioned by Weber, but not figured, belong to the real D. porcellus 
Gosse, not to the species which he figures. That the figure represents the present species is shown 
by the general form, the high, sharp ridge, the single tooth, the form of the trophi, and the exten- 
sion of the anterior edge of the lorica on the left side, all points which are characteristic of the 
present species and distinguish it clearly from D. porcellus Gosse. 
Distribution. — Diurella weberi is not very common. I have recorded it from the following- 
localities: East Harbor, Lake Erie; swamps on North and South Bass islands in Lake Erie, and on 
Presque Isle near Erie, Pa.; Huron River at Ann Arbor, Mich.; a ditch in the tamarack swamp 
region, near Ann Arbor, Mich. 
Weber (1898) found this species in the Botanical Gardens at Geneva, Switzerland, and at St. 
Georges, Switzerland. Mr. F. R. Dixon-Nuttall informs me that he finds it in ponds in England. 
Mr. Charles F. Rousselet has sent me a sketch of what is evidently this species, made from speci- 
mens found in New Zealand. 
4. Diurella intermedia Stenroos (pi. xm, figs. 108-110). 
Synonym: Coelopus intermedins Stenroos (1S98). 
Distinguishing characters. — This species is to be distinguished from Diurella brachyura Gosse, 
which it much resembles, by the tooth at the dorsal anterior edge of the lorica, and by the equal 
toes. From D. weberi , with which it agrees in the single tooth, it differs in the absence of the 
conspicuous ridge and in the equality of the toes. From D. porcellus Gosse it differs in having 
but a single tooth at the anterior edge. From D. sulcata Jennings, finally, it differs markedly in 
the absence of the furrows surrounding the body about the middle. 
External features . — The body is nearly cylindrical, not so short as in D. porcellus Gosse, and 
curved. The head-sheath is set off by a slight constriction from the remainder of the lorica. It 
has nine longitudinal plaits for folding when the head is withdrawn. At the dorsal edge, a little 
to the right of the median line, is a single well-marked tooth. 
The lorica bears no distinct ridge, though a faintly striated area, in some cases apparently 
a little depressed, extends backward from the base of the tooth about half the length of the body. 
Corona . — Corona of usual character. It bears a single sharp dorsal process (pi. xiii, fig. 108) . 
Antenna ;. — The dorsal antenna lies a little in front of the constriction which separates the 
head-sheath from the rest of the lorica. The right lateral antenna lies in the usual position on the 
posterior one-fourth of the body. The left lateral antenna I have not found. 
Foot. — Very short, not pushed so far forward on ventral side as in D. porcellus Gosse. 
Toes (pi. xiii, fig. 110). — The two toes are equal, or so nearly so that one can not be certain of 
a difference in length. There are two substyles, one a little longer than the other, each more than 
half the length of the main toes. 
Internal organs. — The trophi have not been minutely studied. Their general appearance is 
shown in pi. xiii, fig. 108. The gastric glands are very small and fastened to the stomach only by 
slender, thread-like ducts. The other internal organs call for no special remark. 
Measurements . — Total length, about 0.13 to 0.16 mm.; toes, about 0.03 to 0.04 mm. 
History. — This species was recently described by Stenroos (1898). I have found but a few 
specimens, and most of our detailed knowledge of the animal is derived from the notes and figures 
of Mr. F. R. Dixon-Nuttall, which he has with great kindness placed at my disposal. His figures 
are reproduced in figs. 108 and 110. 
Distribution. — I have found only a few specimens, from the Huron River at Ann Arbor, Mich. 
Stenroos (1898) found the animal in Lake Nurmijarvi, Finland. Mr. Dixon-Nuttall informs me 
that examples have often been sent him from Dundee, Scotland, by Mr. John Hood. 
