REPORT ON THE TUNICATA. 
57 
probably clue in great part to tbe contracted condition of the colony, caused by 
preservation in alcohol. The Ascidiozooids are very much shorter antero-posteriorly in 
Sarcohotrylloides wyvillii than in Sarcobotrylloides superhum, and are less regularly 
arranged in systems (compare PI. IT. fig. 12 with von Drasche’s figure). There are 
only eight tentacles in Sarcohotrylloides superhum, while Sarcohotrylloides ivyvillii has 
sixteen. This list of the more notable differences — there are others of less importance — 
shows clearly that these forms constitute two well-marked species. 
I have named the new species Sarcohotrylloides icyvillii in honour of Sir Wyville 
Thomson, who dredged it in the “cold area” of the Fseroe Channel^ close to the famous 
“Wyvdle Thomson” ridge. This region has since been investigated by Mr. Murray 
and Captain Tizard in the “Knight Errant” (1880)^ and the “Triton” (1882), but no 
Compound Ascidians were obtained during these expeditions. 
Sarcohotrylloides wyvillii, n. sp. (PI. IV. figs. 12-18). 
The Colony is of an irregular elongated form and of considerable thickness. The 
surface is somewhat uneven, but smooth. The colour varies from pale pink to light purple. 
The anterior ends of the Ascidiozooids form lighter areas, and the basal part of the colony 
is light grey and semi-transparent. The common cloacal apertures are inconspicuous. 
The lencrfh of the colonv is 4'3 cm., the breadth is 1'6 cm., and the thickness is 
1’3 cm. 
The Ascidiozooids are elongated antero-posteriorly, being about 1‘5 mm. in length, 
and rather less than 1 mm. in greatest breadth. The light area formed on the surface of 
the colony by the anterior end of the Ascidiozooid is about 0'5 mm. in diameter. 
The Test is soft but moderately firm. It is very thick all over the colony. At the 
narrow base it is light coloured and semi-transparent, elsewhere, as seen from the surface, 
it is opaque and of a pale bluish-pink or very light purple colour. No terminal knobs of 
vessels are visible. The test is formed of a homogeneous transparent matrix, in which 
numerous rounded fusiform and stellate cells are imbedded. The vessels are fairly 
abundant, but rather narrow, and they do not branch much. The terminal knobs are 
not very abundant, except just under the surface. 
The Mantle is thin but fairly muscular. The muscle bands are mostly transverse in 
direction, and are very delicate. 
The Branehial Sac is of moderate size. There are three internal longitudinal bars 
on each side. The transverse vessels are moderately wide, and are all of the same size, 
stigmata are regular, and are usually about four in a mesh. 
The Dorsal Lamina is a plain membrane. 
1 See Depths of the Sea, Third Cruise of the “ Porcupine ” in 1869, p. 104. London, 1873. 
2 See Proc. Boy. Soc. Edin., vol. xi. p. 038, 1882. 
(ZOOL. CHAI.L. EXP. — PART XXXVIII. 1885.) Pp 8 
