REPOUT ON THE TUNICATA. 
249 
very different in external appearance from all other known Compound Ascidians (see 
PL XXXII. fig. 8). 
The Ascidiozooids occupy flattened elongated masses varying from 4 mm. to 
3 cm. in length, and from 2 mm. to 8 mm. in breadth at the broadest part. These 
are connected by branching stolons so as to form a rude network (PI. XXXII. fig. 8). 
Probably the stolon was slightly attached to some foreign object, and the remainder of 
the colony lay in a recumbent or semi-erect position. Its sandy condition suggests that it 
probably trailed over a sandy bottom. Each of the flattened masses rising from the 
stolon contains a few Ascidiozooids which may be regarded as forming a system. No 
common cloacal apertures, however, are visible. If present, they are probably placed in 
the middle of the upper end. 
The test does not become thickened in any part of the colony. It merely forms a thin 
but tough skin around each group of Ascidiozooids, and is greatly strengthened by 
imbedded foreign bodies. Some of the Sponge spicules attached to the surface are of 
large size, from 1 cm. to 2 cm. in length. 
The branchial siphon is well formed, and the aperture is surrounded by six elongated 
lobes (PI. XXXII. fig. 10, hr.l.). The sphincter is well developed. The atrial aperture 
is provided with a short languet. The stigmata though not large are well formed 
(PI. XXXII. fig. 9, sg.). The ciliated cells are distinct, and have pointed free ends. 
The rectum is filled with fragments of Diatoms, Sponge spicules, and minute sand grains. 
The ova are large and of a bright yellow colour. The vas deferens is large and 
conspicuous. The spermatic vesicles are rather small and of a pale colour ; they are 
ovate in shape. 
In some of the Ascidiozooids tailed larvse were found in the peribranchial cavity. 
They have each two pigmented sense-organs placed close together near the posterior 
end of the body. Large grouj)s of ectodermal processes are present at the anterior end. 
Psammaplidium Jlavum, n. sp. (PI. XXXII. figs. 11-13). 
27ie Colony is a small irregularly hemispherical mass attached by a wide base. The 
upper end is convex. The colour is a dull opaque yellowish-brown. The surface is even 
but finely roughened all over. 
The length is 1 cm., the breadth 1*5 cm., and the greatest thickness 1‘4 cm. 
The Ascidiozooids are rather small and not very numerous. They are not visible 
until the colony is cut open. The usual size is about 3 mm. in length and less than 
1 mm. in greatest breadth. They are quite opaque and are not divided into regions 
externally. 
The Test is hard and firm, but not tough. It is of a yellowish-brown colour externally, 
but dull grey in the interior of the colony ; it is quite opaque all through. The matrix 
(ZOOL. CHALL. EXP. — PART XXXVIII. — 1886.) Pp 32 
