the ^Challenger ' Monaxonida. 327 



confused, but with broad compact tracts of spicules. Spicules 

 acerate to cylindrical, commonly short and stout. 



Petrosia similisj n. sp. 



Repent, branched, or erect, lobose. Vents large, on upper 

 surface. Yellowish grey. Texture more or less firm, fibrous. 

 Surface smooth. Dermal membrane distinct, supported on 

 ends of primary fibres. Skeleton, of primary and secondary 

 fibres forming rectangular meshes. Spicules slightly curved 

 acerates, fairly sharp ; size "225 by '016 millim. 



Localities. Stations 142 and 150, Southern Ocean, 150 

 fath. ; Station 314, off Falkland Islands, 70 fath. (var. massa) ; 

 Station 208, Philippine Islands, 18 fath. (var. compacta). 



Petrosia truncafay n. sp. 



Massive, sessile. Yellowish. Hard and stony, but rather 

 brittle. Surface smooth. Only one vent present in the single 

 specimen, ^ incli in diameter, at the summit of a large tubular 

 projection. Skeleton a' reticulation of stout spiculo-fibre, 

 primary and secondary fibres distinct. Fibre compact, about 

 •1 millim. thick. Spicules short, stout, slightly curved, cylin- 

 drical ; size '17 by "0094 millim. 



Locality. Station 208, Philippine Islands, 18 fath. 



Petrosia Mspida^ n. sp. 



Massive, sessile, lobate, narrowing at base ; with numerous 

 small papillge, each bearing a single small vent. Yellowish 

 grey. Fairly compact, rather brittle. Surface uneven, 

 minutely hispid. Skeleton a reticulation of spiculo-fibre, in 

 which the primary lines are faii'ly distinct, but the secondary 

 very confused and almost obliterated by numerous scattered 

 spicules. Spicules slightly curved acerates, not very sharply 

 but rather gradually pointed ; size '37 by '021 millim. 



Locality. Royal Sound, Kerguelen, 25 fath. 



Genus Reniera (Nardo). 



Skeleton composed of definite rectangular (sometimes tri- 

 angular or polygonal) typically unispicular meshes. Spicules 

 short acerates or blunted acerates. 



Reniera suhglohosa^ n. sp. 



Sessile, subglobular, hollow, thick-walled, with a wide 

 circular opening at the summit. Diameter about 1 inch. 

 Yellowish grey. Texture firm but very brittle, cavernous. 



23* 



