POLYCHETA FROM THE N.E. PACIFIC. 991 
peristomial appendages was not observed. There are three well- 
differentiated regions, the median of which contains two segments 
with bifid foliaceous notopodia, exactly like those described in all 
species of Phyllochetopterus. ‘There is only one strongly modified 
seta in the 4th segment. In the posterior region there is a 
bundle of fine sete in the notopodium, but the neuropodium is 
stated to be without uncini. 
Phyllochetopterus gracilis, as originally described by Grube, 
‘possesses a pai of short peristomial tentacles. It is possible 
that in the cases examined the greater part had been broken off, 
bat Grube thinks this was unlikely. Or they may really be very 
long peristomial appendages, the tentacles being entirely lost. 
The observations are quite inadequate on this important pot. 
The 4th segment of the anterior region appears to have more 
than one strengthened seta on each side, though the number is 
not actually given. There are two segments here also in the 
median region, and they are similar in form to those of Spio- 
chetopterus. Vhe posterior region contains segments, the noto- 
podia of which each contains more than one seta; but Grube 
expresses himself as uncertain whether the neuropodium 
contains uncini or not. 
Neither of these forms has ever been rediscovered so far 
as I know, and so these descriptions remain still inadequate 
and uncorrected. But as they stand, I share the opinion of 
de Quatrefages concerning them, that no sufficient cause is shown 
for placing the Adriatic form in a separate genus. The differ- 
ences of the tentacles might be explained as errors of description, 
and the variation of number of strengthened sete in the 4th 
segment is unimportant. The presence or absence of uncini in 
the neuropodium of the posterior segments is a moot point in 
both, but it is probably their extremely small size which enabled 
them to escape detection. 
The next question which arises is whether these two forms are 
similar to those better-known species which are grouped to-day 
under the genus Phyllochetopterus. For that genus is charac- 
terised by the possession of a pair of peristomial appendages, as well 
as the long tentacles, and they may possibly have been overlooked 
by Sars and Grube in their respective discoveries. ‘The numbers 
of enlarged sete in the 4th segment and in the notopodium of 
the posterior segments and that of the segments in the median 
region are not definite generic characters. ‘The structure of the 
segments of the median region of these two forms is identical 
with the type usually associated with Phyllochetopterus. It is 
however, I think, a matter of some importance that these two 
early forms should be rediscovered and their position more 
accurately defined. For the present, the generic name Phy/lo- 
chetopterus must certainly be retained, and I trust it will not be 
necessary to go back to the older genus Spiochwtopterus. But 
in the table of the Cheetopterids which is given by Crossland he 
includes Spiochetopterus as distinct from Phyllochetopterus through 
