NoTT. — On N.Z. ComiJosite Ascidians. 319 



appearance from whatever point it be viewed. These spicules 

 are evenly distributed throughout the colony, being absent only 

 on a small portion near the surface in longitudinal sections. 

 (Figs. 1 and 4.) 



Histologically the test is distinctive. Near the surface is 

 a thin layer of transparent matrix interspersed freely with 

 small test-cells, whose anastomosing fibrils give a slight ap- 

 pearance of irregular striation (tig. 4). Below, this passes 

 insensibly into a structure of very different aspect, the matrix 

 being much reduced by the presence of very numerous bladder- 

 cells, transparent and closely placed (hl.c.). Here, as above, 

 the test-cells are smaller than among the Leptoclinids, but are 

 thickly scattered through the small amount of matrix sepa- 

 rating the bladder-cells. A few spicules {s-p.) are also seen; 

 but it is impossible to exactly define their position. This con- 

 dition of test prevails, with slight modifications, throughout 

 the lower layers. 



A few cloacal canals of small size are observable in the 

 test (fig. 2, ex.) ; otherwise it is solid throughout. 



The zooids (fig. 1) are small, and present features of some 

 importance. They are distinctly divided into thorax and ab- 

 domen, but do not show any special oesophageal constriction, 

 as met with among the Leptoclinids. The abdomen is in all 

 cases much larger than the thorax, and far less opaque. 



The branchial siphon is produced into six faint lobes at 

 the branchial pore. It is short and fairly broad, dilating only 

 slightly at the circlet of tentacles (fig. 1, hr.s., and fig. 8. Cf. 

 fig. 8 with corresponding figures in other plates). 



Four rows of branchial stigmata are present, and are in 

 most cases faintly visible through the mantle. The fringing 

 cells are very distinct (fig. 7, /.c), as are also the nuclei of 

 cells lining the branchial vessels. The transverse vessels are 

 peculiar. A transverse lamina (fig. 7, l.t.) runs along the 

 course of each, and, being of opaque nature, shuts out from 

 view the uppermost fringing cells of the branchial stigmata 

 immediately below. This lamina is probably muscular, as 

 faint traces of striation are observed. The longitudinal vessels 

 are fairly wide. 



The endostyle is horse-shoe-shaped in section, and does 

 not exhibit any traces of columnar cells. Its course is straight 

 above and undulating below (figs. 2 and 8, en.). The peri- 

 pharyngeal band is usually very distinct (fig. 8, 2^2^-b.). 



The dorsal lamina is represented by a series of languets, 

 which are, like the buccal tentacles, short and stout (fig. 1, d.l.). 



Nerve ganglia (ii.) and neural glands (n.g.) were seen in 

 transverse sections distinctly (fig. 8), also frequently dis- 

 cernible through the mantle in sections taken longitudinally. 



The alimentary canal is simple. The stomach is thick- 



