ROTATORIA OF THE UNITED STATES. 
299 
CLASSIFICATION. 
The classification of the Rattulidce has been in a very confused condition. There 
is little agreement as to the division of the family into genera or as to the names 
which are to be used for the genera. The specific names are in an equally unsatis- 
factory condition. 
In the present paper the writer attempts to nse the names, both generic and 
specific, which are in accordance with the rules of nomenclature adopted by the 
International Congresses of Zoology. Tn view of the approach ing publication, by 
the German Society of Zoologists, of a systematic review of the entire animal king- 
dom, “Das Thierreich,” in which these rules are to be applied, it seems impossible 
that any names not in accordance with these rules can long persist. While it is of 
course inconvenient to be compelled to change some names that have come into 
rather general usage, the confusion so caused will not last long, and it will be a 
great advantage to get the nomenclature once established on a generally recognized 
basis. In the case of the Rattulidce the confusion is already so great that the adop- 
tion of the names required by the recognized rules of nomenclature can scarcely be 
called even an inconvenience. 
I shall give in the following a brief historical review of our knowledge of the 
Rattulidce, with the purpose of showing the generic names which must be used. 
Historical review. — The first of the Rattulidce to be described was Rattulus 
rattus, by Eichhoru, in 1775. Eichhorn called it the “ Water Rat” (“Die Wasser- 
Ratte”). In 1776 Muller gave it the name Trichoda rattus. The genus Trichoda 
included a heterogeneous group of microscopic organisms, of which the animal at 
present under consideration by no means formed the type, so that the genus Triclioda 
does not belong to the Rattulidce. Muller described also Rattulus car hiatus under 
the name “ Triclioda rattus vesiculam gerens ,” and a third species of the Rattulidce, 
Trichoda lunar is, which it seems impossible now to recognize. In the same year 
(1776) Schrank gave the name Brachionus cylinder ic-m to Rattulus rattus Muller. 
The name Brachionus had already been used for the rotifers which still bear that 
name, so that it is not available for the Rattulidce, and the specific name cylindricus 
is a synonym of rattus. 
In 1786 Muller described Diurella tigris as Trichoda tigris — the specific name 
tigris thus of course having priority for this species. 
Schrank next described Rattulus longiseta , at first (1793) under the name Brach- 
ionus rattus; then (1802) under the name Vaginaria longiseta. The type of Schrank’s 
genus Vaginaria was not one of the Rattulidce, so that we may leave this name out 
of consideration. The specific name longiseta evidently has priority for the animal 
under consideration, however, in place of Ehrenberg’s name hiebrnis. 
In 1816 Lamarck founded for Muller’s Trichoda rattus and “ Trichoda rattus 
vesiculam gerens ” the genus Rattulus. This generic name therefore evidently has 
priority over any other for the Rattulidce, and must take the place of the commonly 
used name Mastigocerca for the genus to which Muller’s species (R. rattus and R. 
carinatus) belong. 
In 1820 the same forms were placed by Goldfuss in the genus Trichocerca. This 
name is of course merely a synonym, so far as the Rattulidce are concerned. 
In 1824 Bory de St. Vincent founded for these same animals the genus Mono- 
cerca, giving them both together the name Monocerca longicauda. Both the 
generic and specific names are thus of course synonyms, and must be dropped. 
