84 THE AUSTRALIAN MUSEUM. 



(?) Polyclinum nigrum, n. sp., PI. Pel. I, figs. 1316. 



External appearance. The colony is encrusting and expanded hori- 

 zontally, of roughly ovate form, and with a convex upper surface. The 

 irregular lower surface is attached to some small oyster shells, barnacles, 

 and pieces of stone, which are all more or less grown over by the test. 

 The colour is a very dark slatey or indigo blue, so dark as to be almost 

 black in parts. The upper surface is smooth and glossy. The extreme 

 length of the colony is 10 cm., the greatest breadth about 4'5 cm., the 

 greatest thickness 3 cm., and the usual thickness about 1-5 cm. 



The Ascidiozooids are scattered evenly over the whole upper surface, 

 but are not arranged in systems. They lie at right angles to the surface. 

 They are about 5 mm. in length, the thorax being from 2 to 3 mm. long 

 (fig. 14). The post-abdomen is very short. It gives off a narrow vas- 

 cular appendage, which runs for some distance through the test. 



The test is firm and cartilaginous. Bladder cells are present (fig. 15), 

 and many dark-coloured pigment cells. The test cells are large and very 

 numerous, so that the test looks crowded. The muscle bands are strong 

 and opaque. 



The mantle is rather muscular and is pigmented. Both longitudinal 

 and transverse fibres are present on the thorax, while longitudinal are on 

 the post-abdomen. The atrial siphon is very long, while the branchial 

 is short. The branchial aperture is 6-lobed and the atrial 4-lobed (fig. 14). 



The branchial sac is exceedingly opaque and contracted. The stigmata 

 are very long, about nine or ten times as long as they are wide (fig. 16). 



The dorsal lamina is represented by about half-a-dozen large, strong 

 languets. The most anterior languet is shorter than the rest and wider 

 at the base (fig. 16, a. I.). 



The tentacles are 10 in number, alternately larger and smaller. 



The alimentary canal forms a very long loop (fig. 14). The narrow 

 oesophagus leads to a somewhat cordate, thick-walled stomach, the wider 

 end of which is anterior. The intestine is narrow and thin-walled on 

 first leaving the stomach, and becomes wider and thick- walled towards 

 the posterior end of the loop. It then turns anteriorly and becomes 

 undulating in its course, and then finally straight. It crosses over the 

 oesophagus to reach the dorsal side of the branchial sac. 



TJie reproductive organs lie in the very short post-abdomen, and extend 

 forwards into the intestinal loop. Only male organs were found. 



Locality. There is one specimen of this species in the collection. It 

 is labelled " 72, Naucluse, Port Jackson, John Brazier, F.L.S." 



