ROTATORIA OF THE UNITED STATES. 
333 
Measurements. — Length of body, 0.16 to 0.17 mm.; of toe, 0.14 to 0.15 mm.; total, 0.30 to 
0.32 mm. 
History. — Rattulus car inatus Lamarck seems to have been the second species of the Rattulidce 
that was described. Muller (1786) considered it a variety of Rattulus rattus Muller, and described 
it under the name of Trichoda rattus vesiculam gerens. He thought that the ridge was an egg 
sac; hence, the above name. Lamarck (1816) founded the genus Rattulus for this species and 
R. rattus, considering them as one species — a view which is, perhaps, not fully disproved yet. To 
this species he gave the name Rattulus carinatus, thus evidently basing his description on the 
characteristics of the species having the ridge. The name carinatus has therefore been properly 
used ever since for this species. The animal has been repeatedly transferred from one genus to 
another (see synonymy) , the name Rattulus becoming completely supplanted by Ehrenberg's name 
Mastigocerca. According to the recognized rules of nomenclature this species must be restored 
to the first genus ( Rattulus ) which was founded to contain it. 
Distribution . — In America Rattulus carinatus Lamarck occurs widely distributed in ponds, 
lakes, swamps, and rivers, but is usually taken in small numbers. I have found it as follows: 
Put bn Bay Harbor and East Harbor, Lake Erie; swamps on North, Middle, and Sorith Bass islands, 
in Lake Erie; Huron River at Ann Arbor, Mich.; Portage River, Ohio; Lake St. Clair, Lake 
Michigan, Round Lake, and Pine Lake, near Charlevoix, Mich.; pools at Hanover, N. H.; ditch 5 
miles south of Ann Arbor, Mich.; and in the following inland lakes of Michigan: West Twin Lake, 
Muskegon County; Crooked Lake, Newaygo County, and Chippewa Lake, Mecosta County. 
By other observers it has been recorded as follows: Pond near Bangor, Me. (J. C. S., 1883); 
Shiawassee River at Corunna, Mich. (Kellicott, 1888); Sandusky Bay, Lake Erie (Kellicott, 1896); 
waters connected with the Illinois River at Havana. 111. (Hempel 1898). 
In Europe: Common in England (Gosse, 1889); Ireland (Hood, 1895); Wurttemberg, Germany 
(Bilfinger, 1892); Gr. Ploner See (Zacharias, 1893); near Rostock, Germany (Tessin, 1886); near 
Basel, Switzerland (Ternetz, 1892); near Geneva. Switzerland (Weber, 1898); Tyrol (Dalla Torre, 
1889); Finland (Levander, 1894, and Stenroos, 1898); Galicia, Austro-Hungary (Wierzejski, 1893); 
Hungary (Kertesz, 1894; Daday, 1897); Bohemia (Petr, 1890); Livland, Russia (Eichwald, 1847); 
Kharkow, Russia (Scorikow, 1896). (Many other authors have listed this animal.) 
Also at Sandringham, Australia (Anderson and Shepherd, 1892); in Ceylon (Daday, 1898) ; in 
New Guinea (Daday, 1901). 
28. Rattulus rattus Muller (pi. xi, fig. 100, 101). 
Synonyms: Trichoda rattus Muller (1776 and 1786); Brachionus cylindricus Sckrank (1776); Trichoda cricetus 
Sckrank (1803); Rattulus carinatus Lamarck (1816, in part); Trichocerca rattus Goldfuss (1820); Monocerca 
longicauda Bory de St. Vincent (1824, in part); Monocerca rattus Ehrenberg (1830, 1838); Mastigocerca rattus 
Hudson & Gosse (1889). 
This animal is practically identical with Rattulus carinatus Lamarck, save that it lacks the 
ridge which forms so conspicuous a feature of that species. Some observers (Muller, Lamarck, 
Bory, Dujardin, etc.) have held that R. rattus and R. carinatus are merely varieties or variations 
of the same species. It is possible that this is true; in the lack of positive evidence that one may 
be transformed into the other it will be more convenient to retain the separate names, however, so 
that they may be recorded separately when desirable. 
After study of a large number of specimens of these two species from many different locali- 
ties I am convinced that there is no sharp distinguishing character except the presence or absence 
of the ridge. Yet in general the specimens of R. rattus Muller which I have seen have been larger 
than those of R. carinatus Lamarck and the body not so strikingly fusiform in shape, but more 
equal in diameter throughout. 
In place of the high ridge of R. carinatus the present species has a broad longitudinal area, 
not elevated, which is marked with transverse striations and occupies the same position as the 
ridge in R. carinatus (fig. 100) . The dorsal antenna lies in a notch on the left side of this striated 
area; a little behind it lies the eye (fig. 100). 
The foot and toes are identical with those of R. carinatus Lamarck. 
Measurements.— Length of body, about 0.17 to 0.18 mm.; of toe, 0.13 to 0.16 mm.; total, 0.30 
to 0.32 mm. 
