1903. | POLYCLADS OF THE ‘“‘SKEAT EXPEDITION.” 315 
in fig. 10 of Plate XXIII. The tentacles also in Collingwood’s 
species are much more prominent. The penis is unpaired. The 
body is nearly circular and the sucker median. ‘Total length 
about 5 mm., breadth 4mm. The arrangement of the eye-spots 
is very different from that normally found in Psewdoceros, but I 
cannot find any other characters distinguishing if from that genus. 
At least two other species of this genus are represented in the 
collection. One of these is a very small individual of the 
P. superbus-group (perhaps P. hancockianus); whilst several 
specimens belong to a species coloured exactly as Proceros con- 
cinnwm Coll., viz., they are blue, with orange margin and median 
stripe. They are, however, very much smaller, about 8 mm. to 
10 mm. in length, and of a different shape, not pointed at their 
hinder end, and have small, folded tentacles, whereas Collingwood’s 
species has pointed tentacles. Proceros concinnwm in fact is almost 
certainly a Euryleptid, whilst these specimens aie undoubtedly 
members of the genus Pseudoceros. 
I prefer, however, not to name them at present. 
Family Dirostu1p«. 
ASTHENOCEROS, gen. nov. 
ASTHENOCEROS WOODWORTHI, sp. n. (Plate XXIII. fig. 7.) 
Two specimens, without notes as to colour; but, to judge from 
these spirit-specimens, the species is of a reddish-brown colour, 
darkest on the middle line. 
Length, about .... 17 mm. 
Bread tints scents Ta 35 
Mouth-opening... 7 ,, from the anterior margin. 
SUCKER i ivr tteaioce 1:5 ,, behind mouth. 
The male and female apertures lie in the usual order between 
the ‘ mouth” and sucker. 
The pharynx is large and much folded, its opening being sub- 
median. This feature will serve at a glance to distinguish this 
species from any of the Pseudoceridze. In describing the type of 
the family, Woodworth [16] makes no statement as to the pharynx, 
but, to judge from the figure given, it 1s median or submedian as 
in the present species, 
The body is flat and almost circular; the anterior margin is 
feebly folded, and there is a small group of eye-spots on either 
side of the middle line, but there are no very definite tentacles, 
The prostate body hes in front of the penis. 
In this respect Asthenoceros differs from the type-genus Dipos- 
thus. There are no brain-eyes. 
Only one of the two specimens was cut into sections, trans- 
versely ; the other specimen appears, from an examination of it 
when cleared in oil of cloves, to be quite immature. The speci- 
men serially cut presents certain peculiar features, which I am at 
