SIDERODEEMA. — ESPBRELLA. 211 



the centre, with one small oval tooth at each end, sharply curved, length 

 0-01 millim. 



Geographical Distribution. — Off New Gruinea (' ChaUenr/er'). 

 East coast of Australia : Port Jackson, N. S, W. (Lendenfeld). 



Sideroderma zittelii, n. sp. 



Incrustiug sponges, which attain a thickness of 15 millim. and a horizontal 

 extent of 60 millim. From the surface peculiar tubercles and digitate processes 

 arise, which may attain a height of 15 millim ; these processes have a circular 

 transverse section, and are at the base 6 millim. thick. The surface is con- 

 tinuous, shining. The colour of spirit-specimens is light brown on the surface, 

 greyish in the interior. The rind is very dense, the interior lacunose and soft. 



The sicchton consists of spicule-bundles and scattered spicules in the interior, 

 and a stout cortex on the surface. The cortex consists of two layers — an outer, 

 composed of trichites mostly perpendicular to the surface and chelfe ; and an 

 inner layer, which consists of tangeutially disposed styli and oxea. The 

 spicule-fibres in the interior form a loose network. Of particular interest are 

 very conspicuous spicule-bundles 0-3-0-5 millim. thick, which extend longitu- 

 dinally upward in the digitate processes. They lie just below the cortex, and 

 are situated at regular intervals of 0- 1-0-2 millim. In each process there are 

 twelve to fourteen such longitudinal spicule-fibres. The megasclera are styli 

 and oxea, measuring 1 x 0-016 millim. The former are more numerous ; they 

 sometimes exhibit slight indications of annular thickenings at intervals of 

 0-08 millim. The oxea are slightly curved, and equally sharp-pointed at both 

 ends. The microsclera are trichites and chelre. The former measure 0-15-0-2 

 X 0-005 millim.; the latter are very small isochela?, with a notch in the 

 middle. 



Geographical Distribution.— East coast of Australia: Port Jackson, 

 N. S. W. {Ramsay). 



Genus ESPERELLA. 



Desmacidonidse with small megasclera. Microsclera : palmate 

 anisochelse, and sometimes sigmata. 



Esperella ridleyi, n. sp. 



Dendritically ramifying sponges, which attain a large size. The shape is 

 subject to extensive variations, according to which I divide the species into 

 Several varieties. 



r2 



