EEPOET ON THE THNICATA. 
243 
The Tentacles are long and slender. 
The Alimentai'y Canal forms a long narrow loop. 
The Post-Abdomen is not large. 
Locality . — UnknoTVTi. 
There are about half a dozen irregular and more or less fragmentary colonies of this 
species in the collection. The locality where they were obtained is unknown. 
The shape of the colony appears to be quite indefinite. It forms irregular in crusting 
masses from 1 cm. to 2 cm. in height, and of varying extent and thickness (PI. XXXI. 
figs. 1, 2). No traces of cloacal apertures or of any arrangement of Ascidiozooids in 
systems is visible. The dimensions given in the above description are those of one of 
the larger specimens in the collection, but probably it is not a complete colony. 
The test is penetrated in all parts by sand grains, which are so abundant that the 
colony both outside and in sections looks as if it were merely a mass of sand (PI. XXXI. 
figs. 1, 2). The roughness, the opacity, the colour, and the stifi" and brittle condition 
of the test are all due to the presence of the imbedded sand grains. The investing mass 
around the Ascidiozooids contains more sand than test substance, and the test where free 
from impurities is clear and transparent. 
The musculature of the mantle over the thorax (PI. XXXI. fig. 3, m.h) is rather 
like that of some of the Ascidiidse amongst Simple Ascidians. The six lobes around 
the branchial aperture are very large and distinct (PI. XXXI. fig. 3, hr.). 
The atrial aperture is placed on the dorsal edge, at a considerable distance from the 
anterior end. It is circular and has no lobes on the margin (PI. XXXI. fig. 3, at.) 
A long tapering atrial languet [at.l.) is present on its anterior edge between it and the 
branchial aperture. The transverse muscle bands are placed with regularity on. the 
sides of the body (PI. XXXI. fig. 3, m.h.), but form a network on the ventral edge over 
the endostyle. The mantle is generally very transparent, but in some of the Ascidiozooids 
it is found to be considerably pigmented. 
The transverse vessels of the branchial sac are provided with strong muscle bands 
(PI. XXXI. fig. 4, m.f.), and they are all joined to the mantle by connectives. The 
stigmata at the ventral end of each row become much smaller, so as to allow the 
transverse vessels to expand into large triangular areas. At the dorsal edge of the 
sac the stigmata are not interrupted by a dorsal lamina (PI. XXXI. fig. 4) but pass 
continuously from one side to the other between the languets. 
The endostyle is large and conspicuous. Its course is undulating. The dorsal 
languets are remarkably short and stout (PI. XXXI. fig. 4, l.)\ their ends are blunt. 
The nerve ganglion is large and of elliptical form. It is placed half way between 
the branchial and atrial apertures and just in front of the atrial languet (PI. XXXI. 
fig. 3, n.g.). 
