538 DR. J. E. GRAY ON SPONGES. [May 9, 



**** Defensive spicules oblong, boat-shaped, concave on the sides. 



22. Naviculina. 



Sponge 1 Spicules: — 1. Equibianchorate, unilateral, ob- 

 long, concave, with a marginal rib on each side, and sometimes a 

 central keel-like one, abundant on membane near fascicules of slender 

 spicules. 2. ? 



Naviculina cliftoni. 



Hymedesmia, sp., Bowerb. B. S. i. p. 252, f. 152. 

 Hab. West Australia, Freemantle (Clifto?i). 



IV. Defensive spicules equihihamate, compressed, with a sharp edge, 

 hooked at each end, free in sarcode. 



23. Hamacantha. 



Sponge ? Spicules of two kinds : — 1. Needle-shaped, slen- 

 der. 2. Equibihamate ; hooks and inner edge of shaft sharp- 

 edged. 



Hamacantha johnsoni. 



Halichondria johnsoni, Bowerb. B. S. i. pp. 35, 127, f. 112, 293. 

 Hab. Madeira. 



V. Defensive spicules hihamate, simple, or contorted, without any 

 bianchorate ones intermixed. 



24. Gellius. 



Sponge massive, minutely hispid. Skeleton regularly netted. 

 Spicules of two kinds: — 1. Fusiform. 2. Bihamate, simple, and 

 contorted. 



1. Gellius JUGOSUS. 

 Isodictyajiigosa, Bowerb. B. S. ii. p. 29G. 



2. Gellius robustus. 



Isodictya robusta, Bowerb. ii. p. 304. 



25. Biemna. 



Sponge massive. Skin rough, spiculose. Skeleton irregularly 

 netted ; fibres composed of longitudinal dispersed spicules, covered 

 with a thin coat of horny m.atter. Spicules : — 1. Fusiform. 2. Bi- 

 hamate, simple, or contorted and reversed. 



Biemna peachii. 



Desmacidon peachii, Bowerb. B. S. p. 349. 



See also — 

 Desmacidon constrictus. 



