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THE VOYAGE OF H.M.S. CHALLENGER. 
Distaplia rosea, and may be regarded as occupying a position between them. In 
general shape and pigmentation it agrees with Distaplia magnilarva, while it differs 
from that species and agrees with Distaplia rosea in having comparatively small Ascidio- 
zooids and larvae. The peduncle is rather larger than in either of Della Valle’s species. 
^ If a Distaplia were discovered which was related to Distaplia magnilarva and to 
Distaplia rosea in the reverse way to that found in the case of Distaplia vallii, that is, 
if it agreed in shape and colour with Distaplia rosea but possessed the large Ascidio- 
zooids and larvae of Distaplia magnilarva, then, unless it had some sufficiently important 
characters peculiar to itself, it would be necessary to unite the four species, and 
consider them merely as varieties showing all the possible combinations (AC, AD, BC, 
BD) of the four characters : — A, large Ascidiozooids and larvae, B, small Ascidiozooids 
and larvae, C, dark pigmentation, and D, red pigmentation. Of course such a combina- 
tion as AB or CD would be impossible. The formulae for the three known species would 
be Distaplia magnilarva, AC, Distaplia rosea, BD, Distaplia vallii, BC, and the 
imaginary fourth form would be AD. 
Genus doubtful. 
if) clava, n. sp. (PL XXVII. figs. 1, 2). 
A specimen found at Station 75,^ off the Azores, cannot with certainty be referred 
to its proper position, as it shows no traces of Ascidiozooids. It is an elongated curved 
mass about 4 cm. in length and 1 cm. in average thickness, and was evidently attached 
by the lower end. The opposite extremity is slightly swollen and convex, and thus 
forms a rounded knob on the summit of a thick peduncle (PL XXVII. fig. 1), but the 
entire mass is composed of test. 
The surface is rather rough, and the colour is a dark dull grey, having lighter and 
darker patches on the upper end (PL XXVII. fig. 1). It is tough and cartilaginous, and 
is seen on section to have the same colour and structure all through. 
The test matrix appears structureless, but is densely crowded with test cells 
(PL XXVII. fig. 2, t.c.). These are rather large, and are mostly of more or less rounded 
form. They are not granular, but are usually clear, homogeneous, highly refracting, 
and of a yellow colour. A few fusiform and stellate cells are also present. 
In some parts of the test, especially in the knob-like upper end of the specimen, large 
numbers of pigment corpuscles are found. They are all spherical, ovate, or ellipsoidal in 
shape, and are of large size (PL XXVII. fig. 2, pig.). The pigment granules, which are 
opaque white, are usually confined to one half of the cell. The lighter patches on the 
upper end of the specimen are due to the presence of very large numbers of these 
* Station 75, July 2, 1873 ; lat. 38° 38' 0" N., long. 28° 28' 30" W.; depth, 450 fathoms ; bottom, volcanic mud. 
