EEPOET OX THE TUXICATA. 
63 
Polycyclus lamarcM, n. sp. (PL IV, figs. 1-5). 
The Colony forms a large roimdecl lobed mass of considerable tlnckness. The surface is 
fairly even, and is smooth. The colour is between buff and pale orange. A lighter coloured 
area is found in the centre of each system around the common cloacal aperture, and here 
and there are similar patches between the systems. The circular systems are fairly regular, 
but are very closely placed. The common cloacal apertures are large and conspicuous. 
The length of the colony is 6 cm., the greatest breadth is 4 cm., and the average 
thickness about 1'5 cm. 
The Ascidiozooids are elongated obliquely from the ventral part of the anterior end to 
the dorsal part of the posterior. On an average they are about 1'5 mm. in greatest length. 
The Test is firmer than is usual in the Botryllidse, and is greatly thickened all over 
the colony ; where free from Ascidiozooids it is of a pale bluish-grey tint. The terminal 
knobs of the vessels are not conspicuous, as they are also of a greyish colour. The test 
is composed of a clear homogeneous matrix, in which numerous cells of various sizes and 
shapes are thickly scattered. The vessels are abundant and branch freely, their terminal 
knobs are numerous and large. 
The Mantle is thin. The muscle fibres are very fine and ap|)ear to run irregularly,, 
most of them are more or less transverse in direction. 
The Branchial Sac is large and strong. The transverse vessels are rather narrow, 
and are all of the same size. There are three internal longitudinal bars upon each side. 
The meshes are about square, and contain each three stigmata. The fine longitudinal 
vessels are rather narrow, and the stigmata are of moderate size and regularly arranged. 
The Dorsal Lamina is a plain but rather wide membrane, with its edge somewhat 
corrugated at the anterior end. 
The Tentacles are rather short. There are only eight, and they are all of much the 
same length. 
The Dorsad Tuhercle is a very small and inconspicuous aperture placed near the 
anterior end of the dorsal lamina. 
Locality. — Station 54 (of the cruise of H.M.S. “Porcupine” in 1869); lat. 59° 56' N., 
long. 6° 27' W. ; bottom temperature — 0’3°C. ; depth, 363 fathoms. 
This species is formed for a specimen of Polycyclus obtained during the cruise of 
H.M.S. “Porcupine” in 1869, at Station 54, in the Faeroe Channel, from a depth of 363 
fathoms. It is attached to and has partially grown over a colony of Sertidaria oper- 
culata. It is irregularly lobed at the free end, and the lobes are all rounded, which gives 
the colony very much the appearance (PI. IV. fig. 1) of a specimen of Alcyonium digi- 
tatum. The thickness is so considerable that there can be no doubt as to the propriety 
of separating this and similar forms from the genus Botryllus. 
The general colour is a yellowish-brown. The Ascidiozooids, as seen on the surface, are 
