REPORT ON THE MONAXONIDA. 7X 



Texture soft. Surface minutely hispid. Dermal memhrane distinct, thin, transparent. 

 Pores collected into groups, forming small, more or less circular pore-areas, each 

 containing up to about twelve pores, but generally less. The groups themselves are 

 placed close together, scattered over the surface of the sponge. Diameter of the 

 pore-areas about 0'3 mm., of the pores about 0'07 mm. The pores are placed very 

 close together within the pore-areas, being separated only by narrow strands of 

 tissue. 



Skeleton. — The mass of fil)re on which the sponge is based, and which it encrusts, is 

 coarse, amber-coloured, branching and anastomosing, with a very large proportion of 

 horny matter and a core of tylostylote spicules of the characteristic Esj^erella type. 

 This fibre was certainly dead before the present sponge grew over it, as it projects far 

 beyond the soft j^arts, and the central canals of the enclosed spicules are enlarged ; it 

 appears, however, probable that it belongs to an older specimen of the same species. 

 The specimen has in addition its own proper fibre. There is, however, no dermal reticula- 

 tion. The deeper skeleton consists of a very loose reticulation of spiculo-fibre, very 

 densely spiculous and with very little horny matter. The main fibres are very broad, 

 and as they approach the surface they subdivide and subdivide again, forming spreading 

 tufts of fibres, each ultimate fibre of which breaks up into a brush of separate spicules 

 whose ends project freely beyond the surface of the sponge, penetrating the dermal 

 membrane. The proper fibre of the sponge is probably thus poorly developed owing to 

 the fact that it makes use of the dead skeleton of another sjDonge. 



Spictdes. — (a) Megasclera ; of one kind only, viz., tylostyli (PI. XV. fig. 5), with 

 small head and slightly constricted neck, tapering rather suddenly to a very sharp point 

 and broadest near the apex; size 0"24.5 by 0'016 mm. The spicules mentioned above 

 as occurring in the horny fibre on which, the sponge is based are of about the same 

 length but slenderer, (b) Microsclera ; (1) rather small palmate anisochelae (PL XV. 

 fig. 11), with a long, narrow palm at the large end; length of spicule about 0'025 mm.; 

 (2) rather large, smooth, simple and contort sigmata (PI. XV. fig. 14), measuring about 

 0'12 by 0"0063 mm. The chelate spicules seem to be almost confined to the dei-mal 

 membrane and are not very abundant even there, while the sigmata are plentiful, 

 both in the dermal layer and in the deeper tissues. The sigmata are often found in 

 groups, in which the spicules are placed close together and parallel with one 

 another. 



A noteworthy feature about this species is the absence of a dermal skeleton reticu- 

 lation. In spiculation it agrees closely with Esperella porosa, nobis. The habit of the 

 sponge is very remarkable, the specimen in question having made use of an old and 

 dead skeleton, perhaps of the same species. 



Locality. — Off Bahia, shallow water. One specimen. 



