538 PROF. c. H. o'donoghue: kepoet on 
thin curved spine like the blade of a knife. At its distal extremity it bears 
a set of saw-like dentioulations on one side, over about one-third or one-half 
its length. These vary in number from tooth to tooth from 7-14 and are of 
different sizes on the same tooth. 
The genital and prebranchial apertures lie immediately in front of and 
below the insertion of the gill. The anus is situated just at the hinder end 
of the gill-mesenter}-. 
Notes. This species is represented in the collection by a single specimen 
from Sandy Island. 
Cheesman (30) has described a form, Pleurohranclms (perhaps Berthella) 
ornatus, from New Zealand, but it differs from the animal here described 
in having brownish mottlings on the back and dark brown rhinophores. 
Unfortunately, details of the radula and labial armature are not given. 
According to Bergh (27) the radula of B. [Pleicrobranchus'] 2}liimula has 
100 rows of teeth 150 in a row, or, again (26), the radnla is stated to contain 
120 rows with about 220 in the row, but it is not clear whether the 150 and 
220 in these descriptions refer to the number of pleural teeth on one side of 
the radula or on both. Vayssiere (75), however, while he does not state the 
number of rows in the radula, gives the formula as 140-155 . 155-140, which 
agrees quite closely with that of the present specimen. The form of the 
teeth also falls within the limits of the variations figured by different authoi's 
for this species. The radula, therefore, appears to be somewhat variable in 
constitution. 
The labial armature, as a whole and in its individual elements, and also the 
shell, as noted above, agree with previous descriptions. It would appear, 
then, that the present specimen belongs to the species B. pluiinda, although, 
if the agreement were not so close, I should hesitate to refer it to that species 
on account of its locality. B. plumula, however, had previously been 
recorded from Norway, Great Britain, France, Portugal, the Azores, the 
Mediterranean, and Lower California, so that it is of wide distribution. 
Sub-order ASCOGLOSSA Bergh, 1876. 
(Saccoglossa von Jheriug, 1876; Elysiomorpha Pelseneer.) 
Branchiae or gills are absent or poorly developed. No shell is present. 
The pharynx is mainly adapted for sucking and does not possess jaws. The 
radula is short, uniseriate, and has teeth of a characteristic shape, which, when 
no longer required, are passed down into a sac or ascus lying at the base of 
the pharynx. The central nervous system is composed of 6 or 7 ganglia 
massed around the oesophagus. The otocysts contain only a single otolith. 
Two seminal vesicles are usually piesent. The penis is often armed with a 
spine. 
