of the Genera and Species of the Freshwater Triclads - Smithsonian ...

Index of the Genera and Species
of the Freshwater Triclads
(Turbellaria) of the World
Of the orders and suborders of the class Turbellaria,
the suborder of freshwater triclads (Tricladida
Paludicola or Probursalia) has never been
treated monographically in the sense of modern
systematics. The last revision of the group was
published by Hallez (1894b) at a time when the
taxonomy was based chiefly on external features,
such as the shape of the anterior end, the presence
or absence of tentacular projections and adhesive
organs, and the number and arrangement of the
eyes.
An attempt to present a "natural" taxonomic
checklist of the suborder, considering mainly the
anatomy of the individual taxa, was made by Kenk
(1930a). After discussing the taxonomic value of
various anatomical structures, Kenk arranged those
species that were sufficiently well investigated in a
system compromising two families, Planariidae and
Dendrocoelidae. This arrangement has been, in
the main, accepted and augmented by subsequent
investigators. Kenk, however, omitted from his
system the numerous species of freshwater triclads
which were too insufficiently known to permit their
placement in proper taxa defined by anatomical
characteristics.
The present knowledge of the freshwater triclads
is in a deplorable condition, widely scattered in
the literature. Checklists and reviews have been
Roman Kenk, Department of Invertebrate Zoology, National
Museum of Natural History, Smithsonian Institution, Washington,
D. C. 20560.
Roman Kenk
Introduction
1
published recently for various geographical areas;
for northern Europe by Luther (1961), for the
Netherlands by Hartog (1962), for Japan by
Kawakatsu (1965b, 1969), for the British Isles by
Reynoldson (1967), for Europe by Dahm (1967a),
for the Americas by Ball (1969a), and for North
America by Kenk (1972). Most of these checklists
also exclude the species which cannot be recognized
by ther fragmentary descriptions.
The present index is an attempt to collect all
existing taxonomic information on freshwater triclads,
with particular attention to nomendatorial
questions and to the complete synonymy of the
species, as far as it can be established at the
present time.
In the historical development of the systematics
of the Turbellaria, the concepts of individual
genera underwent profound changes. The genus
Planaria, which now is a valid genus of the
Paludicola, was originally established by Miiller
(1776) to encompass all free-living lower worms.
Thus many species, originally described as species
of Planaria, are now placed into other orders and
suborders of Turbellaria as well as into the Nemertina
or Rhynchocoela. Similarly, the generic name
Polycelis, introduced by Ehrenberg (1831), was
originally applied to all many-eyed turbellarians,
which include terricolous and polyclad turbellarians
in addtiion to some Paludicola. Since the
names referred to Planaria and Polycelis preclude
their availability for future use, it was deemed
proper to list them in the index, with an indica-