142 THE VOYAGE OE H.M.S. CHALLENGER. 



the Rio de la Plata; depth, 600 fathoms; bottom, green sand ; bottom temperature, 37°*2. 

 Three specimens (being the three which we regard as most typical of the species and 

 from which the above description is taken). 



Myxilla nohilis, var. patagonica, Eidley and Dendy (PL XXVII. figs, 13, 13a, 136). 



1886. Myxilla nohilis, var. patagonica, Ridley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, 



vol. xviii. p. 473. 



Sponge massive, amorphous. Size of largest specimen 37 mm. long by 19 mm. 

 broad and 12 mm. thick. Colour in sj^irit light, yellowish-brown. Texture soft 

 and crumbling. Surface uneven, rugose, traversed by meandering furrows, calling to 

 mind the appearance of the Brainstone Coral [Mgeandrina). Dermal membrane distinct, 

 delicate, tran.sparent. Oscula and Pores not observed. 



Skeleton. — (a) Dermal ; very feebly developed, consisting of scattered tylota. 

 (6) Main; a roughly Halichondrioid reticulation of styli, with irregularly rectangular 

 meshes, about one .sj)icule's length in breadth. The rudimentary fibres, which are almost 

 devoid of horny cementing substance, are echinated, more especially at the nodes, by 

 smaller, spined styli, the bases of which rest upon the filjre. 



Spicules. — (a) Megasclera; of three kinds, (l) Basally spined styli (PL XXVII. 

 fig. 13), sometimes verging upon the tylostylote form ; usually more or less curved and 

 tapering gradually to a sharp point at the apex; size about 0*42 by 0*02 mm.; making up 

 the main skeleton. (2) Much smaller styK (PL XXVII. fig. 136), often with distinct heads 

 (tylostylote); entirely spined, but more so at the base than elsewhere; usually straight; 

 size up to about 0'175 by O'Ol mm., echinating the skeleton fibre at the nodes. (3) 

 Tylota (PL XXVII. fig. 13a), long and slender, and with but slightly marked oval heads. 

 The heads are sometimes flattened at the ends (and with a very faint trace of spina- 

 tion ?). Size about 0'3 by 0'006 mm. Occurring scattered in the dermal membrane. 

 {h) Microsclera; of one kind only, viz., tridentate isochelse, with strongly curved shaft, 

 length up to about 0"04 mm. 



i:oca%.— Station 311, January 11, 1876; lat. 52° 45' 30" S., long. 73° 46' 0" W.; 

 ofi' the south-west coast of Patagonia; depth, 245 fathoms; bottom, blue mud; bottom 

 temperature, 46°*0. One specimen (containing a good number of embryos scattered 

 through it) and a few fragments. 



Myxilla nohilis, var. hacillifera, Ridley and Dendy (PL XXVII. figs. 14, 14«, 146). 



1886. Myxilla nohilis, var. bacilli/era, Ridley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, 



vol. xviii. p. 473. 



Sponge massive, amorphous. The largest specimen is irregularly globular in shape and 

 about 25 mm. in diameter. Colour in spirit yellowish-grey. Texture very soft and 

 spongy. Surface uneven, but not hispid. Dermal membrane distinct, very thin and 



