434 COLLECTIONS FROM MELANESIA. 



primary skeleton-fibres ; the canals I have mentioned range in dia- 

 meter from about -07 to - ] 1 millim. This opening of a considerable 

 proportion of the ciliated chambers directly into moderately wide 

 canals agrees with what Vosmacr finds to be the arrangement in 

 many forms of the other Mouactinellid families Renieridse and Sub- 

 eritidae, as well as in a few other forms, viz. his third type (' Antee- 

 keningen over Leucandra aspera,^.,' Leyden, 1880, and Tijdschrift 

 Nederl. Dierk. Vereen. v. p. 144 et seq.). 



67. Iotrochota purpurea. 

 (Plate XXXIX. fig. L; Plate XLII. figs, e-e"".) 



Halichondria purpurea, Bowerbank, P. Z. <$'. Ls7o, p. 293. 



Dr. Bowerbank's specimen (from the Straits of Malacca) is evi- 

 dently quite young ; the present fine series of specimens, both dry 

 and in spirit (numbering upwards of twenty), gives a better idea of 

 the characters of the species. 



The external form is usually that of a cylindrical column, narrow, 

 diminishing gradually in thickness towards apex, viz. from about 15 

 millim. at base to 4 millim. at apex in adult specimens, dividing 

 towards the apex into two or three subequal branches ; it is some- 

 times flattened irregularly near the base ; it occasionally forms a 

 broad palmate frond or irregular erect expansion, or an irregularly 

 honeycombed horizontal mass which may attain a diameter of 65 

 millim. (2^ inches). The surface is broken up into a forest of 

 pointed or ridge-like monticular elevations, 1-3 millim. apart, 1-3 

 millim. high. In the typical specimen (dry) the surface aculeations 

 are only *5 to 1 millim. apart and the same in height. Texture in 

 spirit rather firm, but soft on surface, tough and flexible ; in dry 

 state harsh ou surface, rather brittle : colour in spirit very deep 

 purple, in dry state dark green or pale purple. Skeleton rectangular, 

 consisting of stout compact primary spiculo-fibrcs devoid of visible 

 horny material, 10 to 20 spicules broad, and of similar secondary 

 fibres 1 to 3 spicules broad. Skeleton -spicules smooth, acuate, 

 rather squarely rounded at base, tapering to a sharp point from about 

 five diameters from end; size chiefly "26 by '0063 millim., a few 

 in the interior of the primary fibres -18 by '005 to *00 ( J5 millim. (in 

 the type the prevailing size is -16 by -0127 millim. and the spicule 

 frequently increases in diameter from the base towards the centre). 

 Flesh-spiculc birotulate (not equianchorate, as stated by Bowerbank), 

 shatt very slender ; rotulse small, umbrella-shaped, with four equal 

 curved teeth; length of spicule -01 G to '019 millim. Sarcodo in 

 spirit dark purple, granular : in dry state either dark purple or dark 

 greenish. Large specimens attain a height of about 150 milbm. 

 (6 inches,. 



/Jab. Torres Straits, various localities down to 10 fms. ; Albany 

 [sland, 3-4 tins. ; Port Molle, coral-re< f. 



Distribution. Straits of Malacca (Bowerbank). 



The specimens referred to as being greenish in colour are all dry, 



