90 THE AUSTRALIAN MUSEUM. 



Branchial sac small and not well-developed. Rows of stigmata few, 

 usually three or four (rarely six). 



Alimentary canal united to thorax by a narrow neck. Stomach 

 usually smooth-walled. 



Gonads placed alongside the intestinal loop. Ovary simple ; ova 

 large. Male system consisting of a single large testis, around which the 

 first part of the vas deferens is coiled spirally. 



Gemmation from the pyloric region ; thorax and abdomen of the new 

 Ascidiozooid formed from separate buds. Embryonic blastogenesis rudi- 

 mentary only. 



The Didemnids in the collection seem to require the formation of the 

 three following new species all belonging to the large cosmopolitan 

 genus Leptoclinum. 



Leptoclinum, M. Edw., 1841. 

 For characters, and list of existing species, see " Eevision," p. 630. 



Leptoclinum incanum, n. sp., PL Did. II., figs. 1 6. 



The colonies are small, rounded or cylindrical masses, attached to 

 various branches and other parts of sea-weeds and Polyzoa and other 

 Ascidians (fig. 1). They are very white, opaque, hard, rather smooth, 

 and encrusting. Branchial apertures of Ascidiozooids visible and slightly 

 prominent, and stellate. Occasional irregularly-shaped cloacal apertures 

 are also visible (fig. 3). Length varying, usually from 1 to 2 cm. ; 

 breadth, on the average, about 5 mm. 



Test very densely crowded with an immense number of small, regular, 

 sharp-pointed stellate calcareous spicules (fig. 2). These spicules are 

 especially numerous on the surface and around the Ascidiozooids (fig. 6). 

 No vessels and no bladder cells are visible. The spicules are smaller in 

 this species than in the two following species of Leptoclinum,, but are 

 far more numerous, and consequently the colony is harder, and of a 

 whiter colour. 



The Ascidiozooids are numerous, and vertically placed. There is no 

 regularity in their arrangement. The body is divided into thorax and 

 abdomen. The atrial aperture has a long languet. 



The mantle has strong branchial sphincters, and longitudinal muscle 

 bundles on the thorax. There are retractor muscles from the anterior 

 end of the thorax. 



