66 
THE VOYAGE OF H.M.S. CHALLEHGEE. 
Polycyclus jeffreysi} n. sp. (PL IV. figs. 6-11). 
The Colony is a slightly irregular mass of moderate thickness, which has grown 
upwards from a narrow base. The surface is fairly even and very smooth. The 
colour is a light yellowish-grey on which slight brownish streaks indicate the Ascidio- 
zooids. The base of the colony is more of a transparent grey, with numerous 
opaque white terminal knobs scattered over it. The circular systems are regular, 
and are not closely placed. The common cloacal apertures are in some places fairly 
conspicuous. 
The length of the colony is 3 cm., the greatest breadth is 2 cm., and the average 
thickness about 8 mm. 
The Ascidiozooids are elongated obliquely from the ventral edge of the anterior end 
to the dorsal edge of the posterior end, and the dorsal and anterior regions are nearest to 
the surface of the colony. On an average they are about 2 mm. in their greatest 
length. 
The Test is soft inside. but firm on the surface, and is considerably thickened except at 
the very base of the colony. Where free from Ascidiozooids it is grey and slightly trans- 
parent. At the base the terminal knobs of the vessels are very conspicuous. The test 
matrix is, in most places, clear and homogeneous. The cells are numerous and of various 
shapes. There are many irregularly stellate forms with long delicate branched rays. 
Vessels are not very abundant, and are rather small ; their terminal knobs are 
large. 
The Mantle is thin and membranous, and is remarkable on account of the almost 
total absence of muscle fibres. 
Tice Branchial Sac is very large. There are three internal longitudinal bars upon 
each side. Tiie transverse vessels are moderately wide, and are all of the same size. The 
meshes are elongated transversely, and each contains five or six stigmata. The fine 
longitudinal vessels are very narrow, while the stigmata are unusually wide. They are 
regularly arranged. 
The Dorsal Lamina is a plain membrane. At the anterior end, which is narrow, it 
has a serpentine course, and its edge is usually undulating. 
The Tentacles are moderately large. There are sixteen, eight long and eight short. 
The latter are very small, and usually irregular. 
The Dorsal Tubercle is a small circular aperture placed very close to the dorsal 
lamina. There is no peritubercular area. 
Locality. — Tangier Bay, Strait of Gibraltar, August 5, 1870 ; depth, 35 fathoms. 
' Named after Dr. Gwyn Jeffreys, F.R.S., who was in charge of the “Porcupine” during the first cruise of the 
expedition in 1870 when tliis species was obtained. 
