23 



PLATE X. 



Polymastia bulbosa, Botoerhml: 



Vol. ii, p. 61, ' Mon. Brit. Spongiada;.' 



Fig. 1. — Tbe type-specimen of P. Indhosa from tlie 

 wet preparation, and of the natural size, (a) A young 

 specimen of Dictyocylindrus growing from near tlie 

 base of P. hvlbosa on tlie same fragment of shell. 



Fig. 2. — Represents a small portion of the bulbous 

 body of the sponge exhibiting one of the porous areas 

 with two open jDores, and a small portion of one of the 

 large primary fasciculi of the skeleton at (a). X 80 

 linear. 



Fig. 3. — One of the large fusiformi-acerate spicula of 

 the skeleton. X 150 linear. 



Fig. 4. — One of the minute spinulate, external, 

 defensive spicula. X 150 linear. 



Polymastia eobusta. 



VoL ii, p. 62, 'Mon. Brit. SpongiadiE.' 



Fig. 5. — P. rohusta of the natural size from the dried 

 specimen presented to me by Prof. William King, of 

 Queen's College, Galway. 



Fig. 6. — A view of a portion of the inner surface of 

 the great cloacal cavity of a specimen of P. rohusta 

 dredged by the Rev. A. M. Norman off the coast of 

 Northumberland. The specimen is mounted in Canada 

 balsam. It exhibits in a very satisfactory manner 

 portions of two of the primary skeleton fascicuh, with 



