128 
THE VOYAGE OF H.M.S. CHALLENGER. 
Colony forming a thick 
incrusting mass. 
I 
D. luhrica. 
Distaplia. 
Colony forming a number 
of distinct knobs or 
pedunculated club-shaped 
masses. 
Ascidiozooids and larvae 
of moderate size. 
Knobs with short 
peduncles or none. 
Colour rose-red. 
I 
D. rosea. 
Knobs with well- 
marked peduncles. 
Colour dark violet 
or purple. 
i 
D. vdllii. 
Ascidiozooids and 
larvae very large. 
I . 
D. magnilarva. 
Distaplia vallii, n. sp. (PL XVIII. figs. 1 to 6). 
The Colony consists of one or more rounded or dome-shaped masses or heads 
borne on the summit of well-marked peduncles. The upper surface of the head is convex, 
and its widest part always exceeds the peduncle in diameter. The peduncle is usually 
two or three times as long as the head, and is nearly as wide. At the top it passes 
gradually into the base of the head, and at its lower end it may be united by stolon-like 
processes to the other parts of the colon}^ The surface is even but not very smooth. 
The colour of the peduncle is light grey with a rosy tinge. The head varies from 
red in its lower part through violet and purple to nearly black at the top. 
The length of the head is 7 mm., its greatest breadth is 9 mm. The length of the 
peduncle is 15 mm., and its average thickness 5 mm. 
The Ascidiozooids are elongated antero-posteriorly and are placed vertically in the 
colony. Each is about 2 mm. in length, and has the body divided into two regions (the 
thorax and the abdomen) of nearly equal size. 
The Test is soft. It is of a grey colour, and is fairly transparent. The external layer 
in the head contains a good deal of dark pigment. Small test cells are numerous and of 
various shapes, but there are no bladder cells. 
The Mantle is thin but fairly muscular. The muscle bands are fine but numerous, 
most of them run transversely. In some places the mantle is considerably pigmented. 
The Branchial Sac is large. There are four rows of long stigmata. Each of these 
is crossed by a narrow transverse vessel which does not interrupt the stigmata. 
The Dorsal Lamina is formed of a series of short triangular languets. 
The Tentacles are not large. There are eight of much the same size and some smaller 
intermediate ones. 
