23 



PLATE X. 



POLYMASTIA BULBOSA, Bowerbauk. 



Vol. ii, p. 61, ' Mon. Brit. Spongiadse.' 



Fig. 1. The type-specimen of P. bulbosa from the 

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

 specimen of Dictyocylindrus growing from near the 

 base of P. bulbosa on the 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 pores, 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 ROBUSTA. 



Vol. ii, p. 62, ' Mon. Brit. Spongiadse.' 



Fig. 5. P. robusta 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. robusta 

 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 fasciculi, with 



