TUNICATA. 323 



completely in the tentacles, as well as in other points, that there can be no question of 

 their distinctness. It is, however, exceedingly like the form described by SLUITER 

 from Billiton (Malay) under the heading " Styela data (HELLER) (?)," in 1885. 

 MICHAELSEN, in his revision of HELLER'S types, dealt with Polycarpa elata, HELLER, 

 assured us that SLUITER'S form does not belong to that species and suggested the 

 name P. seriata for it. The agreement of the Ceylon form with SLUITER'S description 

 extends to the gonads, the branchial sac and the dorsal tubercle, but the tentacles are 

 not alike, and there are other differences in detail, so I consider it safest to give the 

 above full description of my specimens under the name P. sluiteri. In the dorsal 

 tubercle this species closely resembles Styela ambonensis, SLUIT., of the "Siboga" 

 expedition. . 



Polycarpa chalmersi, n. sp. Plate V., figs. 22 to 26. 



External Appearance. Shape rounded or quadrate, somewhat flattened ; attached 

 to lumps of coral or to the tubes of the large Foraminifera Ramulina herdmani in 

 such a way that the anterior end, dorsal edge, and a large part of both sides is 

 exposed (fig. 23). Apertures sessile, cross-slit when closed, opening out into short 

 siphons with wide square ends when alive. Surface somewhat creased, produced into 

 roughened lobes about the anterior end. Colour, red and grey when alive, siphons 

 streaked with red and white ; dull bluish-grey in spirit. Size, 1 *8 centime, x 1 '3 

 centims. x 6 millims. 



Test thin, but tough and leathery, thickening to over I millim. on the roughened 

 anterior end. 



Mantle very thin, closely adherent to test. Muscle bands very fine, forming a close 

 net-work. 



Branchial Sac with four well-marked folds on each side. There are about nine 

 internal bars on a fold, and about three rows of meshes in each interspace (fig. 24). 

 The meshes are nearly square and contain half a dozen stigmata. There are three 

 narrower transverse vessels between each pair of larger ones. 



Dorsal Lamina a plain narrow membrane. 



Tentacles long and slender, of two sizes, about 30 in all. 



Dorsal Tubercle small and simple, in the form of a narrow U-shaped slit, with the 

 opening anterior and placed in a small triangular peritubercular area (fig. 25). 



Alimentary Canal rather short and wide, stomach ridged. 



Gonads small hermaphrodite bottle-shaped polycarps (fig. 26), 10 or 12 on each side. 



Localities: (1) Station XLL, 12 miles south of Galle, 100 fathoms, several 

 specimens; (2) Station XXXV., Galle Bay, 7 fathoms, four specimens on a bit of old 

 coral (fig. 22). 



These specimens show the change which may occur of an Ascidian which is bright 

 red in life into a bluish-grey colour when preserved in alcohol. I have noticed this so 

 frequently in both simple and compound Ascidiaiis that when, in a preserved 



2 T 2 



