146 Mr. H. J. Carter on Specimens 



first-formed parts, and follow the structure on by description 

 and illustration to the full development of the spicule, finally 

 giving a magnified view of the form of the filigreed termina- 

 tion characteristic of each species. 



Discodermia papillata 7 n. sp. 

 (PL VIII. fig. 48, a-L) 



Surface even, discophorous, disks horizontal ; structure 

 papillated throughout, accompanied by a bacillar microspined 

 flesh-spicule (PI. VIII. fig. 48, a, b, c). Colour yellow 

 internally. Outer layer of last-formed disks more or less 

 circular, micropapillated in the upper, and bearing the rudi- 

 ment of a spine (the shaft) in the centre of the lower surface, 

 the smallest disk observed being circular, and about 1-B00th 

 inch in diameter (fig. 48, b and d) ; the next layer larger and 

 more indented on the margin ; after this the disk becomes 

 branched, the spine or shaft fully formed (fig. 48, e), and the 

 papillae enlarged and extended over the branches (fig. 48,/) ; 

 finally the staple spicule of the interior is produced (fig. 48, «'), 

 where the shaft may be observed to be trifidly divided and 

 subdivided until it ends in the filigree, with which it inter- 

 locks with its neighbours (fig. 48, k Jc k) on all sides by 

 botryoidal or grape-like terminations (fig. 48, I) — the original 

 papillae, now still more enlarged and extended over the shaft 

 and branches, presenting over the former a wart-like appear- 

 ance (fig. 48, «'), probably influencing this character of the 

 development throughout, — a similar development taking place 

 at the inner end of the shaft, by which, both on the outer 

 and inner side, the filigree is interlocked with corresponding 

 portions of similar spicules ; and thus the structure presents 

 internally an increase of bulk by successive layers, as the 

 breaking-up of a piece of fully-formed Lithistid testifies. Pa- 

 pillae at first microscopic, finally becoming conical (fig. 48, g). 

 Bacillar spicule elliptical, elongated, microspined throughout, 

 about 3-6000ths long (fig. 48, h). Largest specimen about 

 an inch in horizontal diameter, filling up the depressions of the 

 Melobesian nodule over which it grows, and extending into 

 the crevices and cavities made by excavating sponges that may 

 be underneath. 



liab. Marine. On hard objects. 



Log. Gulf of Manaar. 



Obs. I have thus summarily described the development of 

 this discodermid sponge, so that it will not be necessary to 

 repeat it in the other species more than the occasion demands ; 

 at the same time it should be remembered that the varieties in 

 the structure of the elementary parts of a Lithistid are practi- 



