ECTEINASCIDIA AND THE CLAVELINIDiE . 149 



especially the absence of a distinct abdomen, the position 

 of the alimentary canal, and the condition of the test and 

 mantle are certainly of sufficient importance to charac- 

 terize the genus. 



Ed. Van Beneden places one of Sluiter's species, 

 Ecteinascidia dia/phanis, from the island of Billiton, in the 

 Malay Archipelago, in this genus ; and it is evident, as both 

 Sluiter and Van Beneden point out, that this form is very 

 closely related to my E. turbinata, from which it differs 

 chiefly in the colour, the number of tentacles, and the 

 shape of the dorsal languets. The supposed difference in 

 the genital organs, pointed out by Sluiter and by Ed. Van 

 Beneden, probably does not exist. I think now that there 

 can be no doubt I was mistaken in my description of the 

 relation of those parts in Ecteinascidia turbinata, and that 

 the testis is really peripheral, and the ovary central in that 

 species just as in E. diaplianis, and the new species 

 described below. 



The second species from the Island of Billiton, described 

 by Sluiter under the name of Ecteinascidia rubricollis, is 

 separated off by Ed. Van Beneden as the type of a new 

 genus Sluiteria, characterized by the remarkable condition 

 of the dorsal lamina, which (according to Van Beneden) 

 is a membrane with marginal processes* in place of a 

 series of languets, as in all the other Clavelinidse, and by 

 the test having vessels terminating in conical papillae. 

 The other characters given by Van Beneden are only 

 slightly marked, or are shared with a new species described 

 below, which must be placed alongside E. turbinata and 

 E. diaplianis, in the restricted genus Ecteinascidia. 



Some time after the present paper had been written, and 

 read before the Biological Society, and just as it was going 



* This is certainly not indicated in Sluiter's figure, Natuurk. Tijdsch. v. 

 Nederl. Indie, Bd. XLV., taf. II. fig. 4. 



