428 



COLLECTIONS FROM MELANESIA. 



somewhat too wide a scope, it is at the same time true that a resting 

 place or places must be found for those numerous and varied species 

 which are intermediate between the more plainly marked genera 

 Desmacidon, Esperia, and My. villa. For some of these forms older 

 genera may be employed, e.g. Uirrhopalum(Plocam.ia) for A. coriaceus 

 and rule roc ionides (as I have endeavoured to show in a paper" On 

 the Genus Ploeamia &c," Journ. Linn. Soc, Zool. xv. pp. 481, 482). 

 For some such species (abyssi, phlyctenoid s) Mr. Carter employs 

 the old term Halichondria ; but the type of Fleming's genus Ha- 

 lichondria is Spongia papillaris, Pallas, which appears to be a 

 synonym of Halichondria (Amorphlna, Schmidt) panicea, viz. a 

 Renierid and not a Desmacidine, and so the genus Halichondria, if 

 maintained, should be restricted to Renieridae. 



Amphilectus, it seems to me, may be kept with advantage for 

 forms with dentate or navicular equianchorate fiesh-spicules, with 

 smooth skeleton-spicules and absence of any echinating spicules : the 

 type of the genus is Isodictya gracilis of Bowerbank. It may be 

 perhaps necessary to admit forms in which the tibiella (when pre- 

 sent) is slightly spined, as in Desmacidon anceps, Schmidt. Yosmaer's 

 limitation of Desmacidon to species with horny fibre is not justified 

 by the species he has assigned to it. 



63. Amphilectus tibiellifer. (Plate XLII. figs, t-t" .) 



Erect, massive, sessile by broad base ; sponge broader than high 

 and higher than it is thick, decreasing in thickness towards upper 

 margin, which presents a narrow edge. Sponge-mass honeycombed 

 by a system of tortuous, anastomosing spaces, 3 millim. and upwards 

 in diameter, separated in most cases merely by trabeculae of sub- 

 stance. Surface perforated by the closely-set openings of the above- 

 mentioned spaces ; surface of sponge and of the trabecule between 

 openings even, slightly villous in spirit. Texture of sponge in 

 spirit firm, subelastic, tough ; colour dark reddish umber-brown. 

 Sarcode pale reddish brown, rather soft. Main skeleton consist- 

 ing of compact spiculo-fibre formed of spicule no. 1, showing no 

 horny uniting substance, about 3 to 6 spicules broad, irregular ; 

 some only of the primary fibres go straight to surface, the secon- 

 dary fibres usually meet the primaries at acute angles ; primaries 

 about "5 millim. apart. Dermal skeleton consisting of a network 

 of spiculo-fibre 2 to 4 spicules broad, the spicules mostly loosely 

 aggregated ; meshes of network about '35 millim. apart. 



Spicules : — (1) Skeleton acuate, strong, smooth, straight or slightly 

 curved ; base rather squarely rounded, shaft cylindrical, tapering 

 to point from about three diameters from end; size -38 by -014 

 millim. (2) Tibiella, slender, almost straight; shaft smooth, of 

 same diameter throughout, passing gradually into an oval smooth 

 head about half as thick again as shaft ; size -25 by -0042 millim. 

 (thickness of head) : abundant in dermal membrane and interior. 

 (3) Equianchorate, navicular or shuttle-shaped, with palms rather 



