EEPOET ON THE TUNICATA. 
153 
Branchial Sac formed of a simple mesliwork of longitudinal and transverse 
vessels. No true stigmata present. 
Dorsal Lamina represented by a series of langnets. 
Reprocluctive Organs placed in a long post-abdomen extending behind the 
intestinal loop. 
This genus is formed for an interesting species obtained in the abyssal zone (1600 
fathoms). In general appearance, and in the structure of most of the systems of the 
body, this form agrees with many of the other Polyclinidse, but in the condition of the 
branchial sac it differs from all known sj^ecies of Compound Ascidians, and exactly 
resembles the genera Culeolus, Fimgitlus, and Bathyoncus amongst Simple iVscidians. 
At first I felt inclined, on account of this great peculiarity, to regard this form 
as the type of a new family, but finally I decided to leave it as a very well marked 
genus of the Polyclinidse. Further details and remarks are given under the specific 
description. 
Pharyngodictyon mirabile, n. sp. (PI. XXL figs. 1-18). 
Die Colony consists of a more or less discoid mass, the “ head,” borne on a short 
peduncle. The upper surface of the head is usually flat, and nearly horizontal, while 
the lower tapers somewhat towards the top of the peduncle. The colony is attached by 
the base of the peduncle, which is considerably enlarged. The colour is light grey, with 
a slight yellovflsh tinge about the head. The surface is uneven and not very smooth. 
No common cloacal apertures are visible. 
The length (from top of peduncle to upper surface of head) is 6 mm., and the 
breadth (greatest diameter of head) is 14 mm. The length of the peduncle is about 
15 mm., and its thickness in the middle is 5 mm. 
The Ascidiozooids are exceedingly long, and are placed nearly at right angles to the 
upper surface of the colony. Exclusive of the post-abdomen, containing the reproductive 
organs, the largest measure 4 mm. or 5 mm. antero-posteriorly. Beyond this the post- 
abdomen extends for fully as far again, and reaches into the peduncle. The anterior end 
of the Ascidiozooid is not wide, but a consideralfle part of the body is visible on the 
surface of the colony, forming a mark about 2 mm. in diameter. 
Die Test is moderately hard and Arm. It is fairly transparent, and is of a greyish 
colour throughout. In sections the test is seen to consist of a perfectly structureless 
matrix, in which many small cells are imbedded. The cells are in some places very 
closely crowded. Most of them are round, but fusiform, triangular, and stellate forms also 
occur. They all have large nuclei, which stain very readily. No bladder cells are present. 
The Mantle is moderately strong, and is provided with transverse equidistant muscle 
(ZOOL. CHALL. EXP. — P^VRT XXXVIII. 1885.) Pp 20 
