from the South Coast of Devon. 7 



this order usually possess a large, acerate, long fusiform spi- 

 cule in addition to the rest, there is none in Dercitus niger. 



Stelletta aspera^ mihi, n. sp. PI. IV. fig. 7. 



Massive, spreading, fixed, variable in thickness, following 

 the sinuosities of the rock over which it grows ; compact, 

 rough, and resistant. Surface undulating, even, asperous, of 

 a light grey tint, sometimes cream-colour, occasionally green. 

 Dermal layer (Pi. IV. figs. 7 «, 8 a) colourless, thin, transparent, 

 charged with minute, spinous, sub-bistellate spicules, present- 

 ing here and there, tliough mostly in sheltered parts, groups 

 of large exhalant apertures (oscules) of different sizes, whose 

 orifices are not bordered by an elevated margin, but more or 

 less contracted by a circular expansion of the dermal sarcode 

 extended inwards like the so-called " diaphragm " in Pacliy- 

 matisma ; also minute inhalant apertm-es (pores) scattered over 

 the surface generally, but most evident in the vicinity of the 

 oscules, amidst the projecting ends of the large spicules, which 

 have the peculiarity of lying almost horizontally on the sur- 

 face, and thus imparting to it the asperous character mentioned; 

 in contact internally with the celluliferous layer, Celluliferous 

 layer (figs. 7 Z», 8 />) so thin as to be hardly perceptible, except 

 under an inch compound power, when, in many parts of the 

 surface, the cells of which it is composed may be seen to be 

 arranged in a tessellated manner under the dermal layer ,• and 

 when portions are torn to pieces and placed under a quarter- 

 inch compound power, the cells are found to be imbedded in di- 

 stinct cavities (fig. 14 e), in a kind of sarcodal trama [d] like that 

 of Dercitus niger, and to correspond with them in composition 

 in every particular but the black colour, those of the species 

 under description being colourless. Cells (fig. 14) globular or 

 oval, consisting of a cell-wall, in which is contained a large 

 transparent nuclear (?) body {a) and a small nucleolar (?) one 

 (i), itself apparently nucleated and attached to the larger 

 one ; also containing a great number of free cellules (c), each 

 enclosing one or more colourless granules {/) ; cells not only 

 congregated towards the surface, but scattered throughout the 

 sponge generally, together with here and there a cell with 

 black granules, or "black cell," precisely like those of Dercitus 

 niger ; celluliferous layer in contact with the dermal sarcode 

 extenially, and internally continuous with the body-sub- 

 stance of the sponge. Body-substance (figs. 7 c, 8 c) cream- 

 coloured, densely charged with large, long, acerate spicules, 

 which so project, when it is torn to pieces, as to give it an 

 echinated appearance and equally asperous feel ; composed of 



