TUNICATA. 303 



and is satisfied that his own specimens (from the " Chazalie " expedition) belong to 

 that species. The Australian forms Pera and Peroides of MACDONALD probably also 

 belong to this genus. HARTMEYER, in 1901, re-described with anatomical details 

 EHRENBERG'S Rhodosoma verecundum and STIMPSON'S Rh. papillosum ; and SLUITER, 

 in 1904, in reporting on the Tunicata of the " Siboga" expedition, accepts 

 HARTMEYER'S adequate description as applying to STJMPSON'S brief diagnosis, and 

 refers all his specimens (about a dozen) from nine localities in eastern seas to the 

 species Rh. papillosum, STIMPS. He notes, however, a certain amount of difference 

 between some of his specimens and HARTMEYER'S description. I find also certain 

 points of difference in detail between the Ceylon specimens and the descriptions of 

 HARTMEYER and SLUITER, and, so far as external appearance goes, my specimens 

 when alive agreed rather better with STIMPSON'S three lines on Schizascus petlucidus 

 than with his two lines on S. papillositS. Consequently one course open to me, if I 

 consider my specimens distinct from Rh. papillosum, as re-described by HARTMEYER, 

 would be to refer them to STIMPSON'S 1th. pellucidum and so place my new description 

 under his specific name. But although there is nothing prohibitive of this in 

 STIMPSON'S words, neither is there anything very characteristic that leads us to 

 identify the species without doubt. Consequently, I believe it will be least confusing 

 for future workers, and most conducive to scientific clearness, if the Ceylon specimens 

 are described as a distinct species under a new name, as above. The characters are 

 sufficiently given in the description and shown in the figures on Plate I. The 

 branchial sac (fig. 30) will be seen to differ from both that of Rh. papillosum and 

 that of Rh. verecundum, as figured by HARTMEYER (' Arch. f. Naturges.,' 1901, 

 Beiheft, Taf. iv.). 



Ascidia donnani, n. sp. Plate II., figs. 1 to 9. 



External Appearance. Shape irregularly ovate, posterior end rounded, anterior 

 narrower and truncated. Attached by the posterior half of the left side. Branchial 

 aperture on dorsal part of anterior end, atrial aperture on dorsal edge of body, one- 

 third back ; both apertures somewhat prominent, lobed. Test drawn out into several 

 jagged processes, especially on dorsal and ventral edges (fig. 1). Surface roughened 

 with small asperities. Colour grey (in spirit). Size, 2*4 centims. x 1*5 centims. 



Test thin, cartilaginous ; thickened in places to form the irregular processes shown 

 in the figure. It contains the usual vessels and bladder-cells. 



Mantle with moderately developed musculature and prominent siphons. The 

 atrial siphon is directed backwards, so as to give the body when removed from the 

 test (fig. 2) a somewhat triangular shape. Under the microscope the muscle bands 

 are seen to narrow very abruptly (fig. 7) and end in fine bundles of connective-tissue 

 fibres spirally coiled. 



Branchial Sac with rather large square meshes containing each about half a dozen 

 long narrow stigmata (fig. 5). The transverse vessels are mostly narrow and nearly 



