1048 The American Naturalist. [December, 
2. ON THE IDENTITY OF PRocoTyYLA FLUVIATILIS LEIDY AND 
DENDROCGELUM LACTEUM OERSTED. 
Procotyla fluviatilis was first described by Leidy’ in 1852 under the 
name of Dendrocelum superbwm Girard. In Stimpson’s Prodromus? 
(1858) we find for the first time the form under Procotyla fluviatilis 
Leidy M S. with the synonym Dendrocelum superbum Leidy (non 
Girard). Stimpson’s nomenclature evidently being taken from manu- 
script notes of Leidy, but Leidy himself did not use the name Procotyla 
fluviatilis until 1885. In 1893 Girard” in an exhaustive paper on 
- North American Turbellaria makes a new species out of Leidy’s first 
description, which was not his (Girard’s) D. superbum, calling it Pro- 
cotyla Leidy (with the synonym Dendrocwlum superbum Leidy (non 
Girard), and also retains P. fluviatilis as a second species of Procotyla. 
In other words, Girard in the same work under two different names 
gives two different descriptions of the same species. He thus adds 
greatly to the confusion existing in our knowledge of North American 
Turbellaria. When our Turbellaria become better known there is 
reason to believe that the existing large list of species will be much 
reduced. 
A careful study of the structure of Procotyla fluviatilis has convinced 
the writer that this, one of the commonest of our freshwater planarians, 
is identical with the widely distributed Dendrocelum lacteum Oersted 
of Europe, and that the genus Procotyla should be abandoned. It was 
predicted by Hallez™ that Procotyla would be eliminated when its 
internal structure should become known. The anatomy and histology 
of Dendrocelum lacteum has been most carefully worked out by Iijima.” 
His account and figures agree in every way with the American form, 
as does also the older account of Oscar Schmidt." The variation in 
7 Leidy,J. Corrections and Additions to former Papers on Helminthology. 
Proc. Acad. Nat. Sci."Philad., Vol. V, pp. 288-289, 1 
name of Dendrocælum supatbuin Girard. In Stimpson ’s® Prodromus 
8 Proc. Acad. Nat. Sci. Philad., Vol. IX, pp. 23, 1857. 
®Leidy, J. Planarians. The Museum, Vol. I, No. 4, p. 5. Philadelphia, 
18 
ai Girard, Ch. Recherches sur les Planariés et les Némertiens du l Amérique 
du Nord.. Ann. Sci. Nat., Zool. Tom., XV, pp. 164-166, 1893. 
u Hallez, P. Catalogue des Turbellariés (Rhabdoceelides, Triclades et Poly- 
clades) du Nord de le France, ete. Revue Biol. du Nora de la France, T. IV 
No. 11, p. 454, 1892. 
12 Iijima, I. Untersuchungen über den Bau pád die Entwickelungeschichte der 
Süsswasser-Dendrocæœlen (Trichleden). Zeitschr. wiss. Zool., Bd. pp 
9-464, Taf. XX-XXIII, 1884. : 
er Siders O. Unterschungen über Turbellarien von Corfu und Cephalonia, 
Zeitschr. wiss. Zool. Bd. XI, pp. 1-30, Taf. I--IV, 1862. 
