ROTATORIA OF THE UNITED STATES. 
309 
that there were several teeth. These, when the head is contracted, often give an appearance as of 
projecting teeth, though a close examination reveals the incorrectness of this. 
Hilgendorf (1898) described as. Mastigocerca flectocaudatus n. sp. a rotifer which, from his 
description and figure, bears ranch resemblance to Diurella tenuior G-osse. Apparently the author 
himself concluded that the supposed new species was D. tenuior Gosse, for in my copy of Hilgen- 
dorf’s paper the name Mastigocerca flectocaudatus is crossed out and “ Coelopus tenuior ” substi- 
tuted. apparently by the hand of the author. Hilgendorf gives no measurements, his figures are 
not very detailed and are apparently not made with the camera, so that it is difficult to form an 
independent judgment as to the identity of the animal. It will be best, therefore, to accept the 
view that this was D. tenuior Gosse. 
Distribution. — In America: This species is not rare in the vegetation of lakes and streams, j 
have found it in the following localities: Old Channel, between Round Lake and Pine Lake, Char- 
levoix, Mich.; Put-in Bay Harbor and East Harbor, Lake Erie; Long Point, Canada, near “The 
Cottages” ; swamps on North. Middle, and South Bass islands in Lake Erie; Portage River, Ohio; 
Huron River at Ann Arbor, Mich. ; East Sister Lake, Ann Arbor, Mich. ; ditch in tamarack swamp 
region, near Ann Arbor, Mich. Doubtfully reported by Kellicott (1888) from the Shiawassee 
River at Corunna, Mich.; Sandusky Bay, Lake Erie (Kellicott, 1896); waters connected with the 
Illinois River at Havana, 111. (Hempel, 1898). 
In Europe: England (Gosse, 1889) ; Ireland (Glasscott, 1893) ; Gr. Ploner See, Germany (Zacha- 
rias, 1893); Switzerland (Weber, 1898); Bohemia (Petr, 1890): Hungary (Kertesz, 1894). 
Also in New Guinea (Daday. 1901) ; Ceylon (Daday, 1898) ; New Zealand (?) (Hilgendorf, 1898, 
as Mastigocerca flectocaudatus) . 
3. Diurella weberi, n. sp. (pi. i, figs. 11-14; pi. xm, figs. 116 and 117). 
Synonym: Coelopus porcellus Weber (1898), in part. 
Distinctive characters. — Diurella weberi is to be distinguished from its nearest relative, Diurella 
porcellus Gosse, by the single tooth at the anterior edge of the head-sheath, and by the broad, 
rounded projecting plate (see fig. 14) at the left side of the anterior opening — as well as by the 
high, thin ridge. It differs from Diurella brachyura Gosse in the presence of the anterior tooth 
and of the ridge; from Diurella sulcata Jennings in the prominent tooth, the inequality of the 
toes, and the presence of the ridge; from Diurella intermedia Stenroos in the unequal toes and 
the presence of the ridge. Diurella tenuior Gosse, which in technical characters resembles this, is 
easily distinguished from it in practice by the high, thin keel, the shorter body, and the shorter, 
only slightly unequal toes of Diurella weberi. 
External features. — The body is short, and curved in the arc of a circle, much as in Diurella 
porcellus Gosse, though it is not so thick. The head-sheath is indistinctly set off from the rest of 
the lorica by a slight constriction. At the anterior margin of the lorica, to the right of the dorsal 
median line, is a single sharp, prominent tooth. From this tooth there runs backward a high, thin 
ridge, which is transversely striated and extends about two-thirds the length of the lorica (pi. i, 
fig. 12). This ridge is much more prominent than the ridge of Diurella porcellus Gosse. One 
of the most peculiar characteristics of this species is the large, rounded projection from the left 
side of the anterior margin of the lorica. This is especially noticeable in a retracted specimen 
(see figs. 13 and 14); but gives form to the head even in extended animals (see figs. 12 and 117, 
and compare Weber (1898), fig. 2, pi. 20). In retracted specimens a number of folds may at times 
be seen in that part of the head-sheath not formed by the plate just mentioned. 
Corona. — The corona has not been thoroughly studied. It bears a thick dorsal process. 
Antennal . — The dorsal antenna lies in the usual position, to the left of the ridge. The right 
lateral antenna is in the usual place on posterior third of the body; the left lateral antenna is much 
farther forward, only a little behind middle of body and near dorsal side (figs. 14 and 116). 
Foot. — The foot is not quite so nearly inclosed within the lorica as in Diurella porcellus Gosse 
and is not situated so far forward on the ventral side. 
Toes (fig. 11). — The two toes are nearly equal, but the left toe is a little longer than the right. 
Possibly the difference in length is a little less in this species than in Diurella porcellus Gosse. The 
•length of the main toe is about equal to the diameter of the body. Three or four inconspicuous sub- 
styles are found at the base of the toes; these are much less conspicuous than in D. porcellus Gosse. 
