470 COLLECTIONS FROM MELANESIA. 



Internal skeleton formed by a coarse network of loose spiculo-fibre, 

 tte subcortical ends of tbe fibres rising up so as to support the 

 cortex. A strong cortex composed of a zone of chiefly subhorizontal 

 skeleton-spicules united by sarcodic substance, and about -45 millim. 

 in thickness. 



Spicules : — (1) Skeleton spinulate, very large, decidedly curved, 

 tapering gradually to a sharp point; head oval, shaft tapering 

 slightly towards it, forming a decided but slight neck ; size -8 

 by -035 millim. (2) Spinispirular, either delicate^ long, composed 

 of about three bends, which are gradual, so that no part of the whole 

 spicule lies much out of the straight line ; size -05 to -056 by -0016 

 millim. ; or, rather stouter and shorter, with only two bends, size 

 •032 by -0022 miUim. ; in either case about 10 spines to a bend ; 

 spines slender, sharp-pointed, -0022 to -0032 millim. long. 



Eab. Thursday Island, Torres Straits, 4-5 fms. 



The, unfortunately, single and dry specimen measures 35 millim. 

 (1| inch) high by'25 millim. (1 inch) in extreme breadth. 



The species has in the dry state the colour and much of the 

 appearance of S. vagabunda ; both forms of spicule, however, are 

 considerably larger than in that form and the angulation of the 

 flesh-spicule is les? abrupt. It is, however, undoubtedly nearly 

 related to it. 



100. Spirastrella decumbens. (Plate XLIII. fig. c.) 



Incrusting, thin (-5 to 10 miUim. thick). General surface level 

 (except where affected by the inequalities of the substance to which 

 it is attached), glabrous. Colour in spirit grey, slightly tinged 

 with pink. Vents not made out with certainty. Texture tough 

 and leathery. Internal structure very compact ; no large spaces 

 seen, as a rule, in vertical sections. Sarcode dull greenish, sub- 

 transparent, coloured diffusely. Skeleton consisting of loose spicular 

 tracts, about 6 to 10 spicules broad, running obliquely or at right 

 angles to the surface, and occasionally forming slight prominences, 

 protected by the cortex, and of loose skeleton-spicules lying in all 

 directions between them. Cortex consisting of a layer, two or three 

 spicules deep, of the flesh-spicule, lying in almost colourless sarcode. 



Spicules :- — (1) Skeleton spinulate, slender, tapering very gradually 

 to a sharp point, and very gradually also to the head, below which 

 the shaft forms a decided and weU-deflned neck ; head oval, rather 

 pointed at free end, of about the same diameter as the middle of the 

 shaft, viz. -0095 millim. ; length of spicule -35 miUim. (2) Spini- 

 spirular, moderately stout to stout, consisting of two bends, about 

 12 spines to a bend ; spines strong, tapering from broad bases to 

 sharp points, length about '0045 millim. ; length of spicule '025 

 millim., thickness (excluding spines) -0032 to -0063 miUim. 



Hob. Alert Island, Torres Straits, 7 fms. (growing over ar tubular 

 Eetepora). 



This species appears to be more nearly allied in its spiculation to 

 S. (Alcyoniwm) purpwrea, Lamarck, than to any other Indo-Pacifio 

 species, but it differs from it in wanting the magnificent crimson colour 



