600 COLLECTIONS FROM THE WESTERN INDIAN OCEAN. 



the Adriatic. The conuli are more prominent and distant than in 

 that species, and the proportion of horny matter in the fibre is 

 considerably greater. 



APLYSIMD^E. 



Although Pallas and Lamarck cite Ianthella flabellifomus as from 

 the Indian Ocean, I am not aware that the genus has been hitherto 

 shown to occur on the western side of that ocean. 



15. Aplysina fusca. 

 Carter, Ann. $ Mag. N. H. 1880, vi. p. 36. 



A spirit-specimen, agreeing in its more slender fibre (maximum 

 diameter about '7 millim.), especially near the surface, and in its 

 smaller interconular spaces with the Ceylon specimen rather than 

 with that from S.W. Australia, subsequently assigned to the same 

 species by Carter (Ann.&Mag. N". H. 1881, viii. p. 107), which I have 

 seen. In this spirit-specimen the cells which are so numerously 

 congregated in the surface-membrane are not colourless, as in the 

 dry specimen from Australia, but are very granular and of brownish 

 colour; they measure *008 millim. in average diameter, whereas those 

 of the Australian specimen measure about -013 millim. Having re- 

 gard to these differences, it seems to me not unlikely that the latter 

 specimen is specifically distinct. If the expression " hollow " of Mr. 

 Carter's original description denotes fistulose, the present specimen 

 differs from the Ceylon form in being solid (with the exception of 

 the usual spaces between the fibres). 



Hab. Seychelle Islands, 12 fms. 



Distribution. Ceylon, S.W. Australia? (Carter). 



16. Aplysina pallasi. 



? Spongia membranosa, pars, Pallas, Elench. Zoopli. p. 398. 



Columnar masses, generally less than an inch in diameter at their 

 broadest part, and tending to bifurcate early and at acute angles 

 into secondary lobes of a diameter inferior to that of the main body 

 of the sponge ; the ends of the conuli are only about 5 millim. apart, 

 except near the ends of the lobes, where they approach each other 

 more closely ; a single or bifurcate purple-black fibre projects about 

 1 millim. from the end of almost every conulus, replacing the blunt 

 compound fibrillated mass which is characteristic of this part in 

 A. membranosa (see Carter, also Part I. of this Report). Vents 

 oval, 2-4 millim. in diameter, few, at sides of terminal lobes. Con- 

 sistence elastic, very compressible. 



The skeleton-fibre is much branched and anastomoses frequently, 

 and ranges in diameter from about "9 millim. in main fibres to as 

 little as -1 millim. in some subdermal twigs ; those which terminate 

 the conuli are about -3 millim. in average diameter ; the main 

 direction is upwards and outwards : the fibre is firm, compact, tough ; 



