SPONGES.-HALLMANN. 26 1 



Ophlitaspongia tenuis, Carter. 

 (Plate XXXV., fig. i, and fig. 56.) 



1885. Echinoclathria tenuis, Carter, Ann. Mag. Nat. Hist. (5), 



xvi., 1885, p. 355. 



1886. PhakeUia papyracea, Carter, Op. cit. (5), xviii., 1886, 



P- 379- 



1896. Ophlitaspongia tenuis, Dendy, Proc. Roy. Soc. Vict., 

 viii. (n.s.), 1896, p. 37. 



[Not Clathria tenuis, Hentschel, Fauna Sudwest- 

 Australiens, Tetraxonida, ii., 191 1, p. 377-] 



[1887. (?) Antherochalina tenuispina, Lendenfeld, Zool. 

 Jahrb. 1887, p. 789.] 



Sponge flabelliform, thin, stipitate. Surface even. 

 Oscula apparently absent. No dermal membrane. 

 Skeleton: In young parts of the sponge, spongin being 

 yet but scantily developed, the skeleton appears as a 

 more or less ''renieroid''' retictdation which, in the mid- 

 region of the lamina, is irregidarly isodictyal, but which, 

 in vicinity to the surface {owing to the presence there 

 of outwardly-running paucispicular fibres), becomes 

 generally rectangular ; usually, also, longitudinally dis- 

 posed sheaves of spicules, lying in the mid-region, pro- 

 duce an appearance of axial condensation. Later, there 

 is developed in the mid-region a dense plexus of stout 

 horny fibres which to some extent obscure, and perhaps 

 in part ensheath, the spicules of the ''isodictyal" mesh- 

 work; with increase of age, also, the lamina thickens, 

 the excurrent fibres are correspondingly prolonged, and 

 the rectangularly-meshed outer layer is consequently of 

 greater width. Auxiliary tylostyli are scattered inter- 

 stitially in variable number, generally singly, but also in 

 bundles. Quasi-echinaiing {principal) styli are, as a rule, 

 moderately scarce. Megascleres : — {i.) Curved tapering 

 principal styli. typically more or less fusiform and basally 

 manubriate or sub-basally constricted, shotving signs of 

 a slight differentiation into two kinds, ranging in length 

 from about 75 to upwards of 240 y,, and varying in maxi- 

 mum diameter in different specimens from 8 to 12 y,; 

 {ii.) auxiliary tylostyli, straight or flexuous, with a length 

 of from 160 to upwards of 280 y., and a maximum 

 diameter of j.5 ]i. Microscleres absent. 



