SIGMATELLA. 199 



The colour of the living sponge is greyish brown. The oscula are 1 millim. 

 wide, scarce, and scattered. 



The fibres of the skeleton are composed of large sand-gi-ains. Microsclera 

 strongyla, 0-26 millim. long and 0-003 millim. thick, very abundant. 



G-EoanAPHTCAL DiSTEiBUTioN. — East coast of AustraUa: Port Jackson, 

 N. S. W. {Ramsay). 



Sigmatella corticata, n. sp. 



(The synonyms will be found below in the descriptions of the varieties.) 



The range of form assumed by different specimens of this species, which 

 I have grouped in the five varieties papillosa, mammillaris, elegans, Jlahellum, 

 and serrata, is certainly a very wide one, as, indeed, might be expected, con- 

 sidering that this species is one of the most common sponges in Australian 

 waters. Large adult specimens never appear to be incrusting or massive, 

 although such forms are often assumed by small ones of 8. c. papillosa. Larger 

 specimens of this variety possess more or less fused lobose or digitate processes. 

 Large semispherical protuberances are observed on the surface of the otherwise 

 pretty massive variety of JS. c. mammillaris. The other three varieties are 

 distinctly lamellar. ^S*. c. elegans consists of a much folded, somewhat flower- 

 shaped plate about 8 millim,, thick : the other two varieties are expanded in 

 one plate, and appear flabelliform. S. c.jiabellum is thick, abruptly cut off at the 

 margin with a special marginal face ; >S^. c. serrata is thinner. The margin of 

 this variety appears serrate or dentate, in consequence of the projection from 

 it of digitate processes which are of uniform size and situated radially. The 

 surface is smooth or shagreen-like in aU the varieties, except in S. c. papillosa 

 and >S'. c.jiabellum. In the variety /S^. c. papillosa the surface is always uneven, 

 rugose, tubercular, or covered with a regular network of slightly projecting 

 ridges. The faces of the lamella in S. c. Jlabcllum bear low and irregular pro- 

 jections. The arrangement of the oscula is a very definite one in this variety. 

 In 8. c. papillosa, mammillaris, and serrata the oscula are few in number, large 

 and conspicuous, and situated terminally on the summits of the processes, or 

 scattered irregularly over the surface in small specimens which have no pro- 

 cesses. In S. c. elegans the oscula are small, slightly prominent, and scattered 

 over one face of the lamellae; in S. c. flahellimi they are confined to the 

 marginal face, and are variable in size and pretty abundant. 



The colour of the living sponge is always yellow or red ; particularly ;S^. c. 

 papillosa appears very bright brick-red, whilst the other varieties are more or 

 less orange-coloured. All the varieties are always grey on the surface in the 

 dry state, but often retain the yellow colour in the interior. In the fresh state 



