202 SIGMATELLA. 



laterally, and thus very irregular forms are produced. The surface is always 

 irregular, rugose, tuberculated, or covered with a network of slightly projecting 

 ridges, in the meshes between which fine perforated membranes are observed. 

 The extreme forms are diflferent enough, but they are connected to such an 

 extent by transitions that no distinction can be drawn, particularly as dif- 

 ferent parts of the surface of one and the same specimen often exhibit a very 

 different appearance. I believe that these differences are to a certain extent 

 also due to differences in the mode of preservation of the specimens ; but I 

 have observed that the structure of the surface is also in the case of living 

 specimens subject to great variations. I have for this reason found it advis- 

 able to combine three species of Dysidea, distinguished by Marshall chiefly on 

 account of the difference in the structure of the surface, into this one variety, 

 to which also a number of the specimens in the British Museum labelled 

 Dysidea TcirTcii and Holopsamma lamincf favosa by Carter, belong. However, 

 by no means all sponges so named by Carter belong to it. 



The oscula are large, conspicuous, and few in number. They are always 

 situated on the summits of the processes in the lobose and digitate speci- 

 mens, and occupy prominent positions in the irregularly massive ones. In 

 the small cake-shaped specimens the oscula are irregularly scattered over the 

 surface, and not prominent. They appear to increase in size with the 

 specimens. The oscula of small specimens are only about 2 millim. wide, 

 whilst those of the largest attain a diameter of 8-12 millim. 



The colour of the living sponge is bright brick-red on the surface, dull orange 

 in the interior. Dry specimens are light grey on the surface, but often to a 

 certain extent retain the yellow colour in the interior. 



The anatomical structure of this variety does not present any distinctive 

 features. The description of the canal-system given by Marshall of his Dysidea 

 favosa, which strongly challenges criticism, is discussed above in the description 

 of the species. 



G-EOGEAPHiCAL DiSTKiBUTiON. — European coast: coast of Suffolk (TT. ^. 

 Clarke). 



Coast of Africa : Algoa Bay (Bowerhank Coll.). 



Indian Ocean: Mauritius (Canterbury Museum). 



North coast of Australia : Port Darwin (' Alert '). South coast of Australia : 

 St. Vincent Gulf, S. A. (South Australian Institute) ; Tasmania (Boiverhanlc 

 Coll.) ; Bass Strait (Marsliall) ; Phillip's Island, Port Phillip, V. (Boston Soc. 

 Coll.); Port Phillip Heads, V. (B. Wilson); Port Phillip, Y . (Lendenfeld) ; 

 "Western Port, V. (Lendenfeld). East coast of Australia: Port Jackson, 

 N. S. W. (Lendenfeld, Ramsay). 



New Zealand (British Museum Coll.). 



