SPONGES. 183 



projections, one at least of which bears at its summit a small group of vents through 

 which the radiating canals open, while another bears no visible apertures at all. The 

 upper surface also bears one very small digitiform process, about 5 millims. long and 

 '2 millims. in diameter, with no visible opening, and there may have been more of 

 these processes, now broken off. The texture is hard and compact, almost stony, and 

 the colour (in spirit) is dull brownish -grey. 



R.N. 68 is similar in general features, but the upper surface is much more strongly 

 convex ; the broad, mound-like projections are rather better developed, but still few 

 in number (about three, grouped in the middle of the upper surface), and one bears a 

 conspicuous vent. The slender digitiform processes without visible openings are more 

 numerous than in R.N. 152. Greatest diameter of specimen 34 millims. 



R.N. 182 is a small hemispherical specimen only about 15 millims. in diameter, 

 with the convex upper surface produced in the middle into a single stout digitiform 

 process, about 11 millims. long by 6 millims. thick, but of irregular shape. This 

 process contains wide canals which enter it from the body of the sponge. There are 

 apparently none of the slender digitiform processes. I have seen no vents, but the 

 specimen is somewhat damaged. 



R.N. 202 is closely similar to the last, but rather larger, with a single stout 

 digitiform process in the middle, containing longitudinal canals, but now broken 

 short. 



R.N. 134 is a small specimen about 26 millims. in diameter, with slightly conulose 

 surface and two very short but stout finger-like processes. 



R.N. 77 is much larger than any of the preceding, and the base, instead of being 

 flat below, has grown partially round several loose calcareous nodules. It is strongly 

 convex and more or less conulose and corrugated above, and the upper surface also 

 bears two or three well-developed, stout, erect digitiform processes, very irregularly 

 distributed. These processes contain more or less well-developed longitudinal canals, 

 but there are no visible vents. On the general surface of the sponge the usually low 

 conuli are in places elongated to form slender projections about 4 millims. long, and 

 with strongly hispid surface. The base of this specimen is about 78 millims. long by 

 35 millims. in greatest breadth. One of the larger processes is about 26 millims. 

 high by 1.5 millims. broad at the base, tapering upwards almost to a point, 



From the above descriptions it would appear that the sponge is normally cushion- 

 or cake-shaped, with the upper surface conulose or rugose, and sometimes bearing 

 processes of two kinds, viz., (1) large processes which appear to contain the exhalant 

 canals and to be produced by elongation of low, mammiform, vent-bearing projections, 

 with the conspicuous vents probably replaced by a cribriform dermal membrane ; and 

 (2) small slender processes produced by elongation of the surface conuli, and apparently 

 bearing no special relation to the canal system. 



The main skeleton in the body of the sponge consists of a very dense and confused 

 reticulation of scattered spicules lying in all directions and varying greatly in form 



