E.EPOET ON THE MONAXONIDA. 57 



Genus Trachytedania, Eidley (PI. XXIIL). 

 1881. Trachytedania, Ridley, Proc. Zool. Soc. Lond., January 4, 1881, ji. 122. 



Styli, in part or all, spined. 



The first species of the genus was obtained by the " Alert " in Portland Bay, Chili ; 

 in it the characteristic spination of the stylote spicule, which distinguishes this genus from 

 the closely allied genus Tedania, is only very faintly marked. The Challenger adds one 

 new species, from off the south-west coast of Patagonia, in which the spination of the 

 stylus is very strongly marked ; it is, however, an open question whether this character 

 is in itself sufficient to separate the two genera ; Vosmaer,^ however, accepts the genus 

 Trachytedania as distinct. We have found it advisable to make some alterations in the 

 generic diagnosis. 



Trachytedania patagonica, Eidley and Dendy (PI. XXIIL figs. 6, 6«, Gh, Gc). 



1886. Trachytedania patagonica, Ridley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. 



p. 336. 



Sponge represented by two small, irregularly shaped specimens ; massive, amorphous. 

 Length of largest fragment about 37 mm. Colour in spirit pale yellow. Texture soft 

 and crumbling. Surface uneven, with slight traces of hispidation. Dermal membrane 

 thin but distinct. Oscula (?) small, scattered. Pores scattered; in some parts of the 

 dermal membrane almost or entirely wanting, in other parts fairly abundant. 



Skeleton. — Very loose and irregular, consisting of a somewhat " Isodictyal " reticula- 

 tion of spicules, chiefly of sf)ined styli, but with a small admixture of oxea (toruota). 

 No distinct fibre. Immediately beneath the dermal membrane are a number of irregular, 

 divergent tufts of oxeote (tornote) spicules, while similar spicules are scattered through 

 the dermal membrane itself, forming, together with some of the stylote spicules, a very 

 sparse and irregular dermal reticulation. 



Spicides. — (a) Megasclera; of two kinds — (l) Eather stout, slightly curved, spined 

 styli (PI. XXIIL figs. 6, 6a, G6) ; spined all over, except perhaps at the extreme apex ; 

 but with the spination most marked at the base ; size about 0"35 by 0'0125 mm. (2) 

 Straight, short oxea (tornota) (PI. XXIIL fig. 6c), stoutest towards the centre and 

 tapering gradually to a slightly hastate point at each end; size about 0'245 by O'OOZ 

 mm. Both the form of these spicules and their position in the sponge show that they 

 are homologous with the " bicapitate cylindrical " (tylota) in the typical Tedania, and 

 with the corresponding " cylindricals " of Trachytedania spinata, Eidley.- (h) Ilicro- 

 sclera ; very fine, scattered, oxeote rhaphides, slightly thicker at one end than at the 

 other; length about 0"2 mm., often (? always) spined near the Ijroader end with fine 

 spines directed towards that end of the spicule. 



1 Porifera, Bronn's Klasi?. u. Ordn. d. Tliierreiehs, p. 340. " Prnc. Zool. Soc. Loncl, .January 4, 1881, p. 123. 



(zoOL. CHALL. EXP. — PART Lix. — 1887.) Nnn 8 



