34 GEODIA. ISOPS. 



to eight such spherical ones joined in one mass, which may attain an extent of 

 100 millim. Colour in spirit very dark brown, nearly black. The cortex is of 

 a darker colour than the interior. Surface shagreen-like and very uneven, 

 roughened by projecting ridges and knobs, which are raised 0-8-1-2 millim. 

 over the general surface of the sponge. The oscula are situated in groups at 

 the base of shallow depressions. Ectochonoe pretty nan-ow. Cortex 0-48 

 millim. thick. Below this, exceptionally few canals of the subdermal system 

 are found ; these attain a diameter of 0-24 millim. 



Skeleton. — (1) Tetraxon Mer/asdera. Angles between centripetal and tan- 

 gential rays >90° ; centripetal ray 1-5 x 0-04 millim., slightly conic, and 

 abruptly but not sharply pointed ; tangential rays 0-16 x 0-03 millim., slightly 

 curved, conic, sharp-pointed. These spicules are met with just below the 

 cortex ; they are not numerous. — (2) Mona.ron Spicules. In radial slightly 

 oblique bundles just below the cortex, more irregularly disposed in the in- 

 terior. kSmaller monact spicules are also found in the cortex. The large 

 spicules of the interior are tylostyli, slender, slightly curved, 2 x 0'016 millim., 

 cylindrical, and pretty abruptly pointed. The monact spicules of the cortex 

 are styli, disposed irregularly, cylindrical, and not very sharply pointed ; they 

 measure 0"lx0'08 millim. These spicules form dense masses in the outer- 

 most layer of the cortex. — (3) Polyact Spherical GlohosteUate Spicules. Highly 

 granular ; diameter 0*067 millim. ; forming a dense layer in the cortex, with 

 the exception of the oscular area. Similar spherical spicules are found in great 

 abundance throughout the interior. Here there are also a great number of 

 their young stages. The globostellates in the interior are more spiny than 

 those in the cortex. — (4) Stellate Spicules. The stellates are not at all numerous 

 in this species ; they are of one kind only, small, with numerous slender and 

 smooth rays. 



Geogeapuical Distribution. — East coast of Australia : Broughton Island 

 {Ramsay). 



Genus ISOPS. 



Geodidse the inhalant pores and osciila of which are free and 

 not covered by sieve-membranes. Ectochonse bell-shaped, deep. 

 Globostellates present in all parts of the cortex. Spicules of the 

 interior monact. Various varieties of stellate microsclera present. 



Isops sollasi, n. sp. 



This species grows in the shape of a thick-walled, pedunculate cup, or 

 irregularly curved lamella. The smaller specimnns in pnrticiilar are very 



