DENDY NON-CALCAREOUS SPONGES 121 



There are two kinds of microxea ; (1) covered with small sharp spines; more 

 or less sharply angulated in the middle; size about 0-15 by 0-006 mm.; (2) smooth, 

 but with a distinct swelling at one side of the central angulation (subcentrotylote) ; 

 of about the same length as the spined ones but much more slender, even when 

 allowing for the absence of spines. An intermediate form may occasionally be 

 found, but on the whole the two kinds seem to be fairly distinct. It is possible, 

 however, that the smooth ones may be merely young forms of the other. 



I refrain from giving a name to this species until better material is forth- 

 coming. 



Register Number, Locality, &c. XVIII. 4 a, Channel W. of Beyt Island, 3-4 

 fms., January 7, '06. 



33. Esperella plumosa (Carter). (Plate I., Figs. 4a-4g ;. Plate III., Fig. 19). 

 Esperia plumosa Carter [1882, 1887]. 

 Esperella plumosa Dendy [1905]. 

 Not Esperella plumosa Arnesen [1903]. 



This appears to be a very common and characteristic Indian Ocean species 

 and is by far the most abundant sponge in Mr. Hornell's collection. It was also 

 abundant in Professor Herdman's Ceylon collection. As yet, however, no figures, 

 either of the external form or of the very well developed spiculation, have been 

 published, and it seems desirable to make good this omission on the present 

 occasion. 



The external form appears to be very characteristic, though varying much 

 according to the stage of growth. The sponge seems to begin life as an irregular 

 crust, which becomes 'massive and then grows out into long, flattened, tongue- 

 shaped processes, finally breaking up into slender, pointed, digitiform branches ; or 

 possibly such branches may be formed first as outgrowths of the massive crust, 

 and subsequently fuse to form the flattened tongue-shaped portions. One of the 

 best pieces is represented of the natural size in Fig. 19, but this is not the largest 

 specimen. 



The irregularly conulose or cactiform surface also seems to be characteristic. 

 The surface is subglabrous between the conuli and the dermal reticulation of 

 spicular fibre appears to be very unequally developed ; in one specimen which I 

 have dried it is quite conspicuous in some places, under a pocket lens, while 

 apparently absent in others. The oscula are represented by larger and smaller 

 circular apertures scattered here and there between the conuli. 



Most of the specimens are now, in spirit and dry, of a dull reddish colour, 

 but I suspect that this may be due to their having been preserved in the first 

 instance in formalin. 



I have nothing further to add to my previous description of the skeleton arrange- 



