66 SUBEEITES. — PLECTODENDEON. 



The Australian specimens lead a similar mode of life to the European 

 Suherites domuncula ; they always form the abode of a crab ; I have, 

 however, not seen them enclosing a shell inhabited by a Pacjurus. 

 The largest Australian specimens measure only 35 millim. in breadth and 

 15 millim. in height. The surface is smooth. The colour is bright yellow. 

 Between the surface-tufts of spicules tangential canals are found 0*2 millim. 

 below the surface ; these are irregular and measure on an average 0'14 millim. 

 in diameter ; farther down i-adial canals of equal dimensions are seen, which 

 belong to the exhalant system ; they join to form canals of irregular shape, 

 which are 1 millim. wide; these are not rare in the interior and pour their 

 contents into the wide and short oscular tube. 



Skeleton. — The skeleton consists of irregular masses of tylostyli which 

 form a reticulate structure; towards the surface they are united to very 

 short bundles, which extend to form the surface-tufts ; the spicules of the 

 surface-tufts protrude 0*18 millim. beyond the surface, with their pointed 

 end ; so that, as O. Schmidt remarks, " Die Oberfliiche ist glatt, fiihlt sich 

 aber rauh an." Spicules 0'7x 0-008 millim., cylindrical, gradually and 

 sharp-pointed at one end, and slightly constricted below the bulb, which 

 is spherical and measures 0*014 millim. in diameter ; the bulb is situated a 

 little below the termination ; the truncate end of the spicule appears as a slight 

 centrally situated excrescence of the bulb. 



Geogkaphical Distribution. — Mediterranean. 



Australian Seas : South coast of Australia (Lendenfeld). East coast of Aus- 

 tralia : Port Jackson, N. S. W. (Ramsay, Lendenfeld). 



Genus PLECTODENDRON, nov. gen. 



Pedunculate Suberitidae, forming a regular network extended 

 m one plane. The spicules form very loose, anastomosing bundles. 



Plectodendron elegans, n. sp. 



The whole sponge forms a flabelliform reticulation, which extends in one 

 vertical plane and is attached by a peduncle, 25 millim. long and in the 

 central contracted portion about 12 millim. thick; it widens above and 

 below. The reticulation of the sponge itself is composed of somewhat 

 prismatic trabeculse, which are compressed in a direction vertical to the 

 plaue^ in which the sponge expands; their transverse section is square, 

 with rounded corners, and they measure 9x6-7 millim. in thickness; the 

 meshes of the netvA-ork are elongate, irregularly widened at the ends, and 

 measure 6x25 millim.; fchey are disposed longitudinally. The whole sponge 



