CATALOGUE OP TUNICATA. 75 



Amaroucium distomoides, n. sp., PL Pel. IV., tigs. 713. 



External appearance. The colony is of oblong massive form, attached 

 by a small area at one end and rounded at the other. It is of a yellowish 

 grey colour, and the numerous small yellow Ascidiozooids are con- 

 spicuous over the greater part of the surface. The colony is soft and 

 easily deformed. The length is 7'3 cm., the breadth 3'2 cm., and the 

 thickness T7 cm. 



The Ascidiozooids are small as seen on the surface, and are very 

 numerous. They are arranged in definite systems (PI. Pel. IV., fig. 7), 

 which are in some places circular or stellate in outline, but in other parts 

 become larger and more complicated, and then form branched lines and 

 networks. Cloacal passages are visible in places running through the 

 test. The Ascidiozooids are of an opaque yellow colour, and show dis- 

 tinctly against the grey test. The body is divided into thorax, abdomen, 

 and post-abdomen (fig. 11). The thorax and abdomen are about 2 mm. 

 in length and the post-abdomen may be about 8 mm., or even longer, 

 and very slender. The thorax and abdomen run at right angles to the 

 surface, but the post-abdomen soon turns downwards and runs vertically 

 through the centre of the colony. The post-abdomen terminates in a 

 delicate vascular appendage. The branchial aperture has 6 lobes, the 

 atrial has one large tri-lobed languet. The atrial aperture is dorsal. 



The test is soft. It contains many bladder cells (PI. Pel. IV., figs. 

 8 and 9). There are white pigment cells, and many small stellate and 

 spherical test cells. The outer layer of the test is firmer, and forms a 

 membrane. 



The mantle has muscle fibres running longitudinally over the 

 branchial sac, and also 2 or 3 transverse bands. The mantle is very 

 delicate over the abdomen and strong again on the post-abdomen, where 



there are about 10 longitudinal muscle bands. It is crowded with 

 yellow pigment cells, which, in some Ascidiozooids, are aggregated to 



form stellate and branched masses (PI. Pel. IV., fig. 10). 



The branchial sac has the ventral edge prolonged backwards, so that 



the posterior end of the endostyle projects (fig. 11). There are 3 or 4 



rows of long, narrow stigmata, each about ten times as long as wide. 



The transverse vessels bear horizontal membranes (fig. 12). 



The dorsal lamina is represented by a series of languets set rather 



more than their own length apart (fig. 12). 



The tentacles are 14 in number, alternately large and small. 



The dorsal tubercle is placed close to the base of a tentacle, as there 



is no peritubercular area, and the peri-pharyngeal bands come far 



anteriorly. The opening leads into a wide infundibulum (fig. 13). 



