172 A MONOGRAPH OF THE 



the present circumstances. The dermal tension and de- 

 fensive spicula are exceedingly abundant in all parts of the 

 external surface of the sponge, and so also are the spicula 

 of the skeleton on the membranes on which they are dis- 

 posed. 



14.Hymeniacidon consimilis, Bowerbank. 



Sponge. Sessile, coating. Surface rugose, but not hispid, 

 furnished abundantly with large and prominent 

 mammae. Oscula simple, dispersed. Pores incon- 

 spicuous. Dermis stout ; dermal membrane pellucid, 

 abundantly spiculous, spicula rather short and stout, 

 same as those of the skeleton, depressed, very nume- 

 rous. Skeleton. Abundantly spiculous ; spicula sub- 

 fusiformi-acuate, short, and stout, numerous. 



Colour. Alive, bright orange, sometimes with a tint of 

 green. When dried, externally, greenish gray ; internally, 

 deep red. 



Habitat. Belgrave Bay, Guernsey ; and Herm, between 

 ' tide marks, Rev. A. M. Norman. 



Examined. In the dried state. 



I received six specimens of this species from the Rev. 

 Mr. Norman. The largest was nearly two and a quarter 

 inches in diameter, and rather short of an inch in thick- 

 ness ; the smallest an inch and half in length, by three 

 fourths of an inch in breadth, and rather exceeding half an 

 inch in thickness. The upper surface of each of them 

 was so completely crowded with mammseform bodies as to 

 entirely obscure the dermal surface of the sponge ; in the 

 larger specimens, they were inclined at various angles 

 towards the surface of the sponges, but in the three smaller 

 specimens they were at nearly right angles to the surface. 

 Their normal form appears to be conical, but they are 

 subject to great variations in shape, sometimes being 

 acutely conical about three or four times the height of the 



