REPOKT ON THE TUHICATA. 
281 
The spicules in the test are much more numerous in the upper layer than in the 
deeper parts, and they are most abundant between the anterior ends of the bodies of the 
Ascidiozooids. Consequently in surface view under a low power the Ascidiozooids show 
through as closely placed elliptical areas of a lighter colour separated by bands of opaque 
test densely crowded with spicules. The edges of the lobes around the branchial 
apertures are strengthened with a line of sj)icules, and there is generally a little group 
which forms a thickening at the apex of each lobe. 
The branchial sac is wide, but not long. The stigmata are particularly large and well 
developed (PI. XXXVIII. fig. S,sg.). The transverse vessels vary somewhat in calibre, 
but they are never very large. In some places they are exceedingly narrow, and the 
pointed ends of the stigmata in adjacent rows almost meet (PI. XXXVIII. fig. 8, t?\). 
The ciliated cells are rather small ; their free ends do not project. 
The endostyle, though conspicuous, is not so wide as usual (PI. XXXVIII. fig. 9, e«.), 
and has not the undulating course so common in Compound Ascidians. The dorsal 
languets are narrow. The tentacles are very delicate, but the larger ones are rather 
long (PI. X XX VIII. fig. 9, There are usually eight long and eight short. The 
nerve ganglion is ellipsoidal in form. The ajDerture of the dorsal tubercle is chcular 
(PI. XXXVIII. fig. 7, d.t.). It opens just posterior to the peripharyngeal band, and 
leads at once into a short wide infundibulum. 
The oesophagus runs posteriorly from the branchial sac to open into the globular 
smooth-walled stomach. The intestine is long and forms a widish loop. It presents a 
small dilatation on its course just at its most posterior part. 
Leptoclinum tenue, n. sp. (PI. XXXIX. figs. 8-11, and PI. XL. figs. 3-5). 
The Colony is a small, more or less rounded, incrusting patch. It is thin, and is 
attached by the entire extent. The upper surface is fairly smooth. The colour is pure 
white. 
The length is about 1'5 cm. and the breadth about 1 cm.; the thickness is very 
slight, 0'25 to 0‘75 mm. 
The Ascidiozooids are large and fairly numerous. They are closely and regularly 
placed all over the surface of the colony. Common cloacal apertures are not visible. 
The bodies of the Ascidiozooids are very short. 
The Test is moderately firm, but tears easily. It is of an opaque white colour 
throuarhout. The structureless matrix contains minute rounded test cells and numerous 
O 
calcareous spicules. There are no bladder cells. The spicules are mostly stellate and 
regular, but a. few are nearly spherical or of irregular form. 
The Mantle is rather muscular. 
The Branchial Sac is small, 
(ZOOL. CHALL. EXP. — PART XXXVIII. — 1886.) 
Pp 36 
