spoNGHDA. :,'.>:; 



regularity and straightness of the primaries, the secondaries more 

 constantly form right angles with them, and the meshes are more 

 commonly rectangular. (3) The primary fibres are more or less con- 

 stantly sand-cored ; the core occupies about half the thickness of the 

 fibre. 



In the characters of the purely horny fibre and the size of the 

 meshes decidua agrees with mauritiana; the diameter of the fibre 

 varies from -025 to -063 millim. in the specimen examined (i. e. about 

 the same range as in mauritiana). 



Hub. African Island, Amirantc group, from beach. 



Distribution. Mauritius, Havana (Hyatt). 



It is possiblo that the forms which I have called varieties should 

 rank as distinct species ; but until the arrangement of the soft parts 

 is known I prefer to keep them under one specific heading. Younger 

 specimens of var. decidua have shallower channels, and one has 

 broader tufts and ridges than the rest, thus approaching var. mauri- 

 tiana. The distinctness of the two forms, found at precisely the 

 same spot, shows that the differences between them cannot be due to 

 locality. 



4. Phyllospongia papyracea. 



Spongia papyracea, Esper, Pflanzenth. Fortsetz. ii. p. 38, pi. lxv., 



pi. lxv. A. figs. 1 & 2. 

 Phyllospongia papyracea, Ehlers, Espersch. Spong, p. 22 (? Hyatt, 



Mem. Bost. Soc. ii. p. 543, pi. xvii. fig. 31). 



A dry specimen, 195 millim. (7| inches) high by 155 millim. 

 (6g in.) in greatest lateral extent. It is proliferous, a single base 

 giving rise to the main frond, which is irregularly flabelliform, and 

 to a few smaller strip-like fronds, some of which unite with each 

 other by their edges at a short distance above the base ; main frond 

 also proliferating by giving off at or near its margin, and in one 

 instance from the face, a few small secondary fronds similar in 

 character to the smaller fronds which arise from the base. Vents 

 few, near margin on both front and back of large fronds, diameter 

 1 millim. Primary fibres "(^-"OSS millim. in diameter ; secondary 

 fibres about -035 millim. thick; both devoid of foreign bodies. Some 

 minute intermediate fibres or dense strands of sarcode are also pre- 

 sent. Meshes of main skeleton about *15 millim. wide, of dermal 

 skeleton -18-*28 millim. A few scattered foreign bodies in the 

 dermal fibres. In other respects it agrees with Esper's figure, and 

 his and Ehlers's descriptions. The latter writer says of the fibres 

 of the Esperian specimens that they are " homogeneous," which may 

 fairly be taken to imply that, as in this specimen, they contain no 

 extraneous matter. Hyatt, however, assigns to this species speci- 

 mens (from the Cape of Good Hope) which, from his description, I 

 understand to contain a large amount of foreign material in the 

 primary fibres. 



Hob. Mozambique. 



Distribution. Tranquebar (Espter). 



2q 



