EEPORT OK THE TXJKICATA. 
187 
and tlie simple loop characteristic of Aplidium and Amaroucium. Consequently I 
question the great value of the intestinal tvust as a diagnostic character, and I feel 
inclined rather to put my trust in a combioation of characters, which are ; — The separa- 
tion of thorax, abdomen, and post-abdomen, and the somewhat lateral position of the 
latter, the twisting of the intestine, and the smooth-walled stomach. In regard to the 
last-named character, on which I would lay some stress, Savigny figures a perfectl}^ smooth 
stomach in all his species of Polyclinum, and all the species which I have examined, 
and which seem to me to belong to this genus, have the stomach-wall smooth and free 
from aU folds or irreguilar thickenings, an unusual condition in the Polyclinidse. Con- 
sequently I have come to consider this simple type of stomach as one of the most 
important if not the primary characteristic of the genus Polyclinum. 
Giard subdivided the genus, according to the condition of the systems, into (l) 
Aurantium, in which they are compound, and (2) Polyclinum proper, in which they are 
simple. According to this classification, all of the Challenger species, with the exception 
of Polyclinum pyiiformis, would probably be placed under Aurantium, but, as it is 
exceedingly difficult, if not indeed impossible in some cases, to determine with certainty 
the condition of the systems in specimens presemmd in alcohol, I have considered it best 
for the present to regard Polyclinum and Aurantium as forming one group. When the 
species described below come to be examined afterwards in the living condition, those of 
them with compound and irregular systems can, if their investigator confirms my suspi- 
cions as to their condition, be transferred to the genus Aurantium, leaving Polyclinum 
pyriformis as the sole representative of Polyclinum in the Challenger collection. 
The new species may be distinguished by the following characters : — 
Systems simple 
and distinct, 
{Polyclinum). 
I 
P. i^yriformis. 
Polyclinum. 
Systems compound 
and irregular. 
{Aurantium). 
Test not incrusted Test incrusted 
with sand. with sand. 
Post-abdomen 
distinctly pedunculated. 
I P. fungosum. 
Post^ahdomen not 
distinctly pedunculated. 
Post-ahdomen 
attached to 
ventral edge of 
intestinal loop. 
Post-ahdomen 
attached to 
posterior end of 
intestinal loop. 
Stigmata 
minute and 
inconspicuous. 
P. incertum. 
Stigmata 
large and 
well developed. 
P. depressum. 
P. molle. 
P. minutum. 
