CATALOGUE OF TUNICATA. 45 



The dorsal tubercle is very remarkable (fig. 10). It shows what 

 seem to be caeca of the neural gland, and meandering lines under a 

 thin membrane. If there are any apertures they are very minute and 

 difficult to find. 



Polycarpa stephenensis, n. sp., PI. Cyn. XVII., figs. 1 5. 



External appearance. Shape oblong, almost quadrangular, attached 

 by wide posterior end, and flattened laterally. Apertures at dorsal and 

 ventral edges of anterior end. Surface a little corrugated and somew r hat 

 encrusted with shells, &c. Colour greyish yellow. Length 10 cm., 

 breadth 6 cm., thickness 2 cm. 



Test leathery but rather soft ; thickened up to nearly 2 cm. at the 

 posterior end, thin elsewhere ; vascular and rather cartilaginous in its 

 thicker parts. 



Mantle thick, yellow r , opaque, but not muscular. There are no strong 

 muscle bands, but numerous thin fibres running in all directions to 

 form a close felting. 



BrancMal sac with 4 well-marked folds on each side. There are 6 

 internal longitudinal bars on a fold and 4 in the interspace ; the bars are 

 wide and ribbon-like. The transverse vessels are all rather wide, but 

 occasional much w r ider ones occur. The meshes are much elongated 

 transversely, and may contain as many as 12 of the small stigmata. 



Dorsal lamina a plain narrow membrane, slightly curled round. 



Tentacles large, numerous, and closely placed. There are about 45 to 

 50 of the longest size, and at least the same number of smaller ones 

 between. 



Dorsal tubercle cordate, almost circular in outline, with both horns 

 turned in. 



Gonacls very many small polycarps imbedded in the mantle on both 

 sides of body. 



Locality. Port Stephen ; one specimen. 



This large species grows erect from a slightly spreading base of 

 attachment (PL Cyn. XVII., fig. 1). Its surface has scattered over it a 

 number of specimens of a small Serpulid Annelid, and towards the 

 posterior end a few shell fragments, etc., are attached. The test is soft 

 for a Polycarpa, and between coriaceous and cartilaginous in texture. A 

 large vessel enters it from the mantle near the posterior end, and breaks 

 up into the numerous ramifying vessels. 



The mantle and branchial sac are of a yellow colour, and the mantle 

 is thickened up to nearly 1 cm. at the posterior end. The stigmata are 



