52 Mr. H. J. Carter on 



as large. Vents single, terminal, peristomed, at the ends of 

 the conical processes respectively ; all leading into a general 

 cloacal cavity, which is thus rendered wide, irregular, and com- 

 pressed, in accordance with the form of the specimen ; holes in 

 the cloaca numerous, of dififerent sizes and distances apart, the 

 largest more or less sunk into the wall-structure, showing 

 within again the openings of the chambers of the latter ; sur- 

 face of the cloaca smooth, or, if echinated, it is with one of 

 the projecting arms of a triradiate, as there are no quadri- 

 radiates. Wall comparatively thin, composed of largely can- 

 cellated sarcode traversed by equally large triradiates, whose 

 shafts, coming from opposite sides, cross it entirely, and 

 whose widely spread-out arms support the structure of the 

 surface outside and the spicular layer of the cloaca within 

 respectively. Spicules of two kinds, viz. acerate and tri- 

 radiate ; no quadriradiates : — 1, acerates, for the most part 

 long, thin, straight^ and cylindrical; 2, triradiates, regular 

 and irregular, of two sizes, small and large, the latter far 

 exceeding the otlier in this respect, averaging for the shaft 

 225 by 22-6000ths in., with wide-spread arms of nearly the 

 same length, so that it approaches an equiradiate form. 

 No. 1 confined to the peristome, where the shorter spicules 

 are intermixed with the longer ones which are broken 

 off; no. 2 to the surface of the body, the cloaca, and the 

 wall-structure ; those of the cloaca towards the mouth 

 furnished, as usual, with j^a^ arms, which, sagittally expanding 

 across the inner ends of the peristome-spicules, bind 

 the latter down to a common level, as before stated, like 

 the cross bars of a paling, while the shaft, which may be 

 insignificantly short and round, is directed perpendicularly 

 backwards. Size of specimen 1 inch high by 1 x | inch 

 horizontally. 



25. Heteropia 'pluriosculifera. 



Agglomerate. Specimen in form irregularly triangular, 

 rather compressed, consisting of three individuals or lobes, 

 each of which is provided with a peristome; growing on a 

 small branch of a Fucus. Colour whitish yellow externally, 

 sponge-brown within. Surface uniformly composed of mode- 

 rately large triradiates bound together by cribriform sarcode. 

 Pores or interstices of the cribriform sarcode large. Vents 

 single and terminal, situated on the prominent parts of the 

 lobes respectively, each furnished with a peristome ; leading 

 to a common cloacal cavity, corresponding in shape with that 

 of the specimen, but much wider than the wall, which, being 

 only l-33rd inch thick, looks also in this case like a mere shell 



