TUNICATA. 301 



since been separated oft' into the allied genera Riwpalcea, Rhopalopsis, and Sluiteria, 

 there remain seven closely allied species amongst which the present one must take its 

 place; they are -.Ecteinascidia turbinata, Herdman, from Bermuda; E. diaphanis, 

 Suiter, from Malaysia ; E. moorei, Herdman, from Alexandria ; E. thurstoni, 

 Herdman, from the Gulf of Manaar ; E. garstangi, Sluiter, from Mozambique ; 

 E. euphues, Sluiter, and E. psamrnodes, Sluiter, both from the Australian Coast. 

 From all these the present species appears to differ either in external characteristics 

 or in internal structure. The two last-named species were described by Sluiter from 

 Semon's collections, and are very minute forms (the Ascidiozooids being only 2 to 

 3 millims. long) which show some resemblance, as their author has pointed out, to the 

 genus Perophora, and especially to such a species as P. hutchinsoni, Macdonald. 

 The two remaining species of Ecteinascidia, E. nexa, Sluiter, and E. mtdticlathrata, 

 Sluiter, from the " Siboga" expedition, are both somewhat exceptional forms showing 

 an approach in some of their characters to the genus Sluiteria, although differing from 

 that genus in other essential points. From these, and from all other described species 

 of Ecteinascidia* the present species differs notably in having distinct and prominent 

 siphons (Plate I., fig. 9) which give to the anterior end of the body very much the 

 appearance of a Ciona. Another noteworthy feature is the arrangement of the 

 muscles in the mantle (fig. 1 1 ) which is quite unlike that in any other known species 

 of this genus. 



Ecteinascidia seems to be a tropical type of Ascidian structure, occurring, so far as 

 we know at present, only between Bermuda to the north and the north coast of 

 Australia to the south, and having its main development in eastern seas. Out of ten 

 known species, eight occur in the Indian Ocean and Malaysian seas, viz., E. garstangi 

 (Mozambique), E. psammodes (Australia), E. diaphanis (Malay), E. euphues (Malay), 

 E. nexa (Malay), E. mult iclath rata (Malay), E. thurstoni (Gulf of Manaar), and the 

 present new species, E. sluiteri, from the coast of Ceylon. 



I have much pleasure in naming this species in honour of Professor Sluiter, of 

 Amsterdam the author who has described most of the species of this genus. 



Family: ASClDILLLE. 



Rhodosoma ceylonicum, n. sp. Plate I., figs. 24 to 33. 



External Appearance. Body, when retracted, of short cylindrical, ovate, or deep 

 cup-shaped form, with a rounded posterior and a flattened anterior end forming the 

 operculum over the apertures. Attached by the anterior part of the right side just 

 below the test that forms the hinge of the operculum. The siphons are close 

 together and are directed forwards, a slight fold rises behind each siphon (fig. 27). 

 Surface covered with small sharp papilla? on the anterior half, especially round the 



* Such as E. diligens, Sirni'.i:. from the Pacific, which seems an exceptional form, 



