130 Mr. F. A. Bather on a 
their apices or free ends. If Protoscolex was setiferous, it 
follows that the sete were disposed as in the Perichetide, 
and this is what one would expect. The double rows of 
papillae may be compared with the secondary annulation 
eccasionally found in modern forms, and so present no 
difficulty. 
It may be objected that the Oligocheta, especially the 
group to which the Perichzetide belong, are normally 
terrestrial or, at most, inhabitants of fresh water. There is, 
however, & priori reason to suppose that terrestrial oligo- 
chetes were derived from aquatic, and ultimately marine, 
forms. The primitive Phreoryctes lives both in water and on 
land. It is among the Microdrili, with less pronounced 
clitellum, that most aquatic species are found. Thus, some of 
the Tubificide (e. g., Cliteliio and Vermiculus) and various 
Enchytreeids are marine or littoral Among the Megadrili 
there are, at any rate, three marine genera—Pontodrilus, 
Acanthodrilus, and Pontoscolex. 
The rarity of Oligocheta among fossils may be explained 
as due to their softness and easy decomposition. The hypo- 
thetical primitive forms of marine habitat would probably 
have been less easily preserved than the familiar earthworm. 
The paleontologist has to rely on an occasional lucky chance, 
such as the blow that for the first time exposed a Protoscolex 
in the long-exploited beds of the Lower Ludlow formation. 
So soon as the Oligocheta took to fresh waters, swamps, and 
the land, their opportunities of leaving an imperishable record 
were further restricted. 
The only fossils that anyone has hitherto proposed to refer 
to the Oligocheta are “ fiinf braune Abdriicke, welche héchst 
wahrscheinlich den Ringelwiirmern angehdéren,” found in the 
Noeggerathia beds of the Coal Measures near Rakouitz, 
Bohemia, and described as Pronaidites carbonarius by 
J. Kusta (1888, Sitz.-ber. béhmisch. Gesell. Wissensch., 
Math.-nat. Cl., Jahrg. 1887, p. 561, pl. fig. 1). The length 
is a little over 10 cm., diameter 0°5 mm, to at most 2 mm., seg- 
ments (in the holotype, which is 1°5 mm. wide) about U°5 mm. 
high, All specimens are bent, curved, or even twisted. The 
side-contours are not very sharp. ‘Towards one end of the 
holotype a canal runs down the middle of the body ; its 
width is not stated, and it does not appear in the figure. 
In all the given details Pronaidites agrees with Proto- 
scolex, and the measurements of the segments are the same 
as in Protoscolex simplex. Papille are not mentioned, but 
neither are they recorded for Protoscolex simplex, P. tenuis, or 
the genotype P. covingtonensis. The reference of Pronaidites 
carbonarius to Protoscolex is therefore inevitable. 
