66 LIVERPOOL BIOLOGICAL SOCIETY. 
in one Polycarpa, in which the horns are symmetrical, 
and first turn in and then out again—a very unusual 
condition (Pl. VIII., fig. 5). 
In another Polycarpa the tubercle was nearly circular 
in outline, and apparently much complicated by the 
development of lateral branches from the original slit, 
which made the surface appear marked- with rather a 
grotesque pattern (Pl. VIII., fig 4). In such a form it is 
difficult to trace its derivation from a simple circular 
opening. 
Altogether there are thirteen species which we have not 
yet been able to identify. The majority of them evidently 
belong to the genus Polycarpa ; but, on a more detailed 
examination, many of them will, most probably, turn out 
to be new species, which will have to be thoroughly 
described, figured, and named, and we hope to have an 
opportunity at some future meeting, when our work is 
completed, of giving an account of these new species to 
the Society. 
EXPLANATION OF PuatTE VIII. 
Fig. 1. Part of the branchial sac of Boltenia pachyder- 
matina showing spicules in a transverse vessel. 
Highly magnified (800 diam.) 
Fig. 2. Various forms of spicule from the test of Boltena 
gibbosa. Highly magnified. 
Fig. 3. The dorsal tubercle of Polycarpa tinctor. Abnormal 
specimen. Magnified (50 diam.) 
Fig. 4. The dorsal tubercle of an undescribed species of 
Polycarpa. Magnified. 
Fig. 5. The dorsal tubercle of another new species of 
Polycarpa. Magnified. 
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