52 THE AUSTEALIAN MUSEUM. 



Dorsal tubercle very large, triangular in outline, and having the open- 

 ing of the duct broken up into a large number of small simple apertures. 



Locality. Port Jackson ; one specimen. 



This species was in the collection along with some specimens of 

 Polycarpa rigida, from which it differs, not only in internal structure, 

 but also in the external form and in the consistency of the test. The 

 body is more flattened from side to side, and is more narrowed anteriorly. 

 The apertures are remarkable for their wide open condition. The sur- 

 face is not rough, nor minutely wrinkled, nor sandy ; but is marked by 

 low rounded ridges with grooves between, which run mainly longitudin- 

 ally (PI. Cyn. XX., fig. 1). On the left side the body is partly covered 

 by a thin layer of a smooth encrusting sponge, and at the posterior end 

 are attached various pieces of cinder. The test on section shows many 

 little brown dots, which are the dilated knobs on the numerous vessels. 

 At the base of the wide atrial siphon there is a circular fold which bears 

 about 40 atrial tentacles. These tentacles are minute, and their terminal 

 parts are slender, but the bases are swollen so as to be in contact with 

 their neighbours (fig. 5). 



The branchial sac is, like the mantle, of a very dark brown colour ; 

 both are thin, and are closely pressed against the test. Most of the 

 transverse vessels are very narrow (fig. 2) ; usually every 6th or 7th is 

 much wider. The large, soft porous-looking dorsal tubercle is seen in 

 fig. 3, and its condition is magnified about 50 times in fig. 4. Several 

 other species are known, in which the hypophysial duct is broken up 

 into several openings. Herdrnan described Cynthia irregularis with 9 

 openings in 1882. Sluiter has since described, amongst other species, 

 Styela (Polycarpa) pneumonodes (=Ascidia aurata, Quoy and Gaimard), 

 with about 26 openings, and Polycarpa sulcata, Herdrn.,* has also the 

 aperture of the duct broken up ; but the present form has more than a 

 hundred openings, and they are quite closely placed (see fig. 4). 



This form at once recalls Polycarpa sulcata, Herdm., of the " Chal- 

 lenger " collection, and I have come to the conclusion, after a careful 

 comparison, that they are so closely related, as to be at most only 2 

 varieties of the same species. Sluiter's Styela pneumonodes is clearly 

 the same as my P. sulcata, and must therefore lapse, and since writing 

 the "Challenger" Keport, I have become convinced that my species 

 may be referred to the Ascidia aurata of Quoy and Gaimard, and that 

 the correct name for all the above forms is, therefore, Polycarpa aurata, 

 Q. and G. 



* "Challenger" Report, Tuuicata, Pt. I., and also von Drasche, Denkschr. K. Akad 

 Wiss. Bd. XLVIIL, PI, VII., fig. 2. 



