CATALOGUE OF TUNICATA. 89 



Mantle strong, and opaque in the contracted state. The muscle 

 fibres run longitudinally over the thorax. 



Branchial sac rather contracted and opaque. Stigmata rather long, 

 about same width as inter-stigmatic vessels, and about seven times as 

 long (fig. 9). 



Dorsal lamina represented by rather short, thick, dark languets, 

 which are placed one on each transverse vessel (fig. 9). 



Tentacles about 20, of two sizes. There are 6 larger ones alternating 

 with smaller ones, which are placed about two together ; they are all 

 rather small. 



Alimentary canal with a small, simple stomach, and a thin-walled 

 undifferentiated intestine (fig. 8). 



Gonads, with many masses of spermatic vesicles in the post-abdomen, 

 and a very large and conspicuous brown-coloured vas deferens. 



Locality. No label, probably Port Jackson ; about 20 small colonies. 



[The following Polyclinidae have also been recorded from Australian 



seas : 



Sigillina australis, Sav., Port Jackson. 



Atopogaster aurantiaca, Herdm., Bass Str. 



Polyclinum fungosum, Herdm., Port Jackson. 



P. depressum, Herdm., Torres Str. 



P. glabrum, Sluiter, Amboina. 



P. hospitale, Sluiter, Thursday Is. 



Amaroucium albidum, Herdm., Bass Str. 



A. Bitteri, Sluiter, Thursday Is. 



Psammaplidium spongiforme, Herdm., Port Jackson. 



Ps. ovatum, Herdm., Torres Str. 



Ps. pyriforme, Herdm., N. Australia.] 



Family III. DIDEMNID-ffi, Giard, 1872. 



Colony usually flat, thin, and encrusting, rarely thick and massive, 

 never pedunculated. 



Systems complicated and irregular, inconspicuous, or absent. Common 

 cloacal apertures usually conspicuous. 



Ascidiozooids rather small, divided into two regions thorax and 

 abdomen. Branchial aperture 6-lobed ; atrial plain, or provided with an 

 atrial languet. 



Test gelatinous or cartilaginous, usually containing stellate calcareous 

 spicules. Ectodermal processes well-developed and provided with 

 muscle fibres so as to form retractor muscles. 



