44 
THE VOYAGE OF H.M.S. CHALLENGER. 
RemarJts. — Although, the minute characters of the cortex are indeterminable (the 
specimen is a dry one), there can be little doubt that it belongs to the Tetilla type ; 
the presence of trichodal trisenes is strongly in favour of this determination. 
The spreading circular fringe of basal spicules reminds one of Trichostemma 
hemispherica, Sars, it differs from the fringe of this species, however, in several details, 
chiefly in being denser and composed of larger spicules, which again are trisenes and not 
styles. 
Tetilla dactyloidea (Carter.) 
Tethya dactyloidea, Carter, Ann. and Mag. Nat. Hist., ser. 4, vol. iii. p. 15, 1869 ; vol. ix. 
p. 82, pi. X. figs. 1-5, 1872 j and ser. 5, vol. xi. p. 365, 1883. Non 
Ridley, Voyage of the “Alert,” p. 625, 1884. 
Sponge, a highly prolate ellipsoid; with a leash of anchoring spicules proceeding from 
the base ; a single circular oscule at the apex ; pores generally distributed. Surface 
pilose. 
Spicules. — I. Megascleres. 1. Somal oxea, fusiform, exceedingly sharply pointed, 
1’35 by 0*006 mm. 2. Somal protrisene, rhabdome 1*43 by 0*004 mm.; cladi 0*026 
mm. long; chord 0*013 mm., or cladi of different lengths, the longest 0*04 mm. 3. 
Radical anatrisene, rhabdome 12*0 by 0*004 mm., cladi 0*032 mm. long, chord 0*0355 mm. 
II. Microsclere. 4. Sigmaspire, 0*008 mm. long. 
The oxeas are arranged partly in fibres and brushes, partly irregularly scattered. 
Except on approaching the ectosome the fibres are arranged longitudinally, but near the 
ectosome short brushes of spicules, directed at right angles to the surface, radiate 
outwards ; the longitudinal fibres are crossed by the irregularly scattered spicules, and as 
they descend they curve outwards and enter the ectosomal brushes, to the formation 
of which they contribute ; near the base, however, they appear to converge, and 
anatrisenes making their appearance, the fibres issue from the sponge as the leash of 
anchoring filaments. The cladomes of the anatrisenes form a series of successive stages of 
growth within the sponge, evidently growing forwards to replace those of the protruding 
filaments as these become effete. 
Co lour. — Brownish-grey. 
Habitat. — South-east coast of Arabia ; Mergui Archipelago ; Burmah. 
Remarhs . — I owe to Mr. Carter’s generosity a perfect example of this sponge from 
Mergui. It is well enough preserved in spirit to admit of examination in thin shoes; the 
foregoing measurements are based upon it. Whether it is altogether identical with the 
type of the species found off the south-east of Arabia I do not feel quite certain. ' Carter’s 
drawing representing the whole sponge suggests the existence of several important 
