REPORT ON THE MONAXONIDA. • 135 



62 mm. and is about 6 mm. thick ; it is strongly curved. (The colour is now reddish, 

 but this is due to the rusting of the case in which the sponge was packed, which has 

 also affected many other specimens from the same station.) Texture soft and spongy. 

 Surface, on one (the convex) side very rough and uneven, with a worn appearance, on 

 the other slightly rough and longitudinally wrinkled. Pores oval, about 0*03 mm. in 

 long diameter, in irregular groups. 



Skeleton. — (a) Dermal ; the dermal membrane is supported on the ends of brushes of 

 tomote spicules which radiate outwards from below the surface of the sponge ; these 

 spicules may also occur scattered horizontally through the dermal membrane. (6) Main; 

 the main skeleton is a very loose and confused reticulation of large, smooth, stylote 

 spicules, with a tendency towards the fonnation of incipient fibre. 



Spicules. — (a) Megasclera; of two kinds, (l) Large, stout, slightly curved, sharply 

 and gradually pointed, smooth styli (PI. XXVII. fig. 1), size about 077 by 0'04 mm. 

 (2) Hastately pointed, smooth tornota (PI. XXVII. figs, la, \b), size about 0'35 by 

 O'Ol mm.; dermal, {b) Microsclera ; of two kinds, (l) Tridentate isochelas (PL XXVII. 

 fig. Ic), with stout, strongly curved shaft; length up to about 0'04 mm., l)ut more usually 

 about 0'025 mm. ; abundant. (2) Very abundant sigmata, rather stout and often much 

 contort, size about 0"07 by 0'004 mm. 



This species evidently comes very close to Myxillch spongiosa, nobis, from the same 

 station, but is sharply marked oS from it by the form of the dermal spicules (perhaps also 

 by their arrangement), by the greater stoutness of the stylus, and by the diflference in size 

 and shape of the tridentate isochelas, as well, perhaps, as by the general form of the sponge. 



Zoca%.— Station 320, February 14, 1876 ; lat. 37° 17' S., long. 53° 52' W.; off the 

 mouth of the Rio de la Plata ; depth, 600 fathoms ; bottom, green sand ; bottom 

 temperature, 37°"2. One specimen. 



Myxilla crihrigera, Eidley and Dendy (PI. XXVII. figs. 7, 7a, 7b). 



1886. Myxilla crihrigera, Eidley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. p. 472. 



Sponge apparently free ; digitate, consisting of a single long, digitate process arising 

 from a shorter, stouter, transverse piece. Total length of sponge 50 mm. ; length of the 

 transverse piece 31 mm.; diameter of main lobe about 12 mm. Colour in spirit dark, 

 yellowish-grey. Texture soft and spongy. Surface minutely aud irregularly hispid. 

 Dermal membrane very distinct, thin, transparent, often readily separating from the 

 underlying tissues. Oscula small, scattered, with their margins flush with the surface (?). 

 Pores arranged in definite, more or less circular pore-areas. The surface of the sponge 

 presents in many places distinct rounded areas, marking the position of sul)dermal 

 cavities covered over only by the thin, transparent dermal membrane, which is in these 

 places penetrated by very large, oval pores. These cribriform areas, and even the pores 



