ROTATORIA OF THE UNITED STATES. 
329 
Measurements. — Length of body without toe or anterior spines, 0.30 mm.; length of toe, 0.20 
mm.; length of longest anterior spine, 0.06 min.; total, 0.56 mm. 
History. — This is one of the best known of the Rattulidce and has, ever since the time of 
Ehrenberg, gone under the specific name bicornis. though Ehrenberg admitted that Schrank's name 
longiseta was the first one given. 
The animal was first described by Schrank in 1793. He confounded it at that time with Rat- 
fulus rattus, and gave it. therefore, the name Brachionus rattus. In 1802 Schrank recognized the 
distinction between this and Rattulus rattus , and gave the present animal the specific name longi- 
seta, placing it, along with a heterogeneous group of organisms, in the genus Vaginaria. The 
specific name longiseta must, according to the rules of priority, be used for this animal in place of 
Ehrenberg’s name bicornis. Ehrenberg (1830) recognized this animal as Schrank’s species, but 
changed the name to bicornis, because he thought this name more appropriate than longiseta. 
This proceeding is, of course, not a justifiable one according to the rules of nomenclature. 
The only synonym which has been added for the specific name since the time of Ehrenberg is 
the Monocerca cornuta of Eyferth (1878) . There can be no question, it seems to me. that this is the 
same species as Rattulus longiseta (Monocerca bicornis). Eyferth himself seemed of that opinion, 
saying that even if this is the same species as Ehrenberg’s bicornis, the name must be changed to 
cornuta, and giving the new name cornuta with a mark of interrogation. The new name was 
based upon the number of teeth at the anterior edge of the lorica, but Eyferth’s account (1885) of 
these agrees very closely with what may be observed in Rattulus longiseta, save that he considered 
one of the two long spines to be an antenna, an error similar to that which he made in the case of 
Diurella stylata (q. v.). 
Eyferth says that in Monocerca cornuta there is a dorsal ridge, ending in a spine, and that at 
the sides and on the “ chin ” at the anterior edge there are two pairs of smaller points, statements 
which are true for 11. longiseta, as shown in fig. 67. He did not recognize the doubleness of the 
ridge nor of the spine, errors of a character which were frequently made at that time and which 
occur repeatedly in Eyferth’s account of the Rattulidce. Hudson & Gosse (1889, Supplement, 
p. 35) have made quite unnecessary difficulties for the recognition of Monocerca, cornuta Eyferth 
as Rattidus longiseta ( Monocerca bicornis Ehrenberg) by altering and adding to Eyferth’s descrip- 
tion, though their account is supposedly taken from that of Eyferth. They say that the two 
lateral teeth are half the length of the dorsal spine, though Eyferth makes no such statement. In 
Eyferth’s figure the exact position of the real anterior edge of the lorica is not discernible, so that 
the relative length of the spines can not be judged from this. Hudson & Gosse add “no sub- 
styles,” though Eyferth states exactly the contrary. A comparison of fig. 68 of the present paper 
with Eyferth’s fig. 24, Taf. vii (1885), will show at once how such a figure as that of Eyferth could 
he made from the present species. 
The following figures or descriptions of this animal have been given (doubtless the list could 
he increased) : Schrank (1793, 1802,1803) ; Ehrenberg (1830,1838) ; Dujardin (1841 ) ; Perty ( 1852) : Ley- 
dig (1854): Pritchard (1861); Bartscli (1870,1877); Eyferth (1878, 1885): Blochmann (1886); Tessin 
(1886); Hudson & Gosse (1889); Bilfinger (1892); Bergendal (1892); Glasscot.t (1893); Wierzejski 
(1893); Eckstein (1895); Scorikow (1896); Stenroos (1898): Weber (1898); Jennings (1900, 1901). 
Distribution. — In America: Rattidus longiseta Schrank is* common amid plants in lakes and 
streams, though it rarely occurs in large numbers. I have recorded its presence in the following 
places: Put-in Bay Harbor and East Harbor, Lake Erie; marsh on the shores of Lake Erie at “ The 
Cottages,” Long Point, Canada; Huron River at Ann Arbor. Mich.; Lake St. Clair; Chippewa 
Lake, Mecosta County, Mich.; Round Lake and Pine Lake at Charlevoix, Mich; pools at Hanover, 
N. H. Other observers have recorded it as follows: Pond near Bangor, Me. ( J. C. S. . 1883) ; waters 
connected with the Illinois River at Havana, 111. (Hempel, 1898). 
In Europe (only typical localities given) : Germany (Ehrenberg, 1838, and many other authors) ; 
England (Gosse, 1889) ; Ireland (Glasscott, 1893) ; Hungary (Bartsch, 1877) : Greenland (Bergendal, 
1892); Bohemia (Petr, 1890); Russia (Scorikow, 1896): Finland (Levander, 1894); Tyrol (Dalla 
Torre, 1889); Austrian Poland (Wierzejski, 1893); Switzerland (Weber, 1898); Roumania (Cos- 
movici, 1892). 
