208 A MONOGRAPH OF THE 



membrane, probably in consequence of the washing it had 

 undergone previous to being dried for the cabinet. They 

 require a microscopic power of 300 or 400 linear to define 

 them in a satisfactory manner when in situ. 



The occurrence of the inflato-cylmdrical spicula in the 

 dermal membrane of this species might lead a hasty ob- 

 server to imagine the specimen a variety of 7/. virgidtosa, 

 but the difference in the form of the skeleton spicula will 

 readily distinguish them. In the latter sponge both skele- 

 ton and tension spicula are acuate, while in H. ficus the 

 skeleton ones are spinulate, and the tension spicula more or 

 less attenuated acuate. From the great size of the latter 

 it naturally leads to the supposition that the skeleton spicula 

 are of two forms, instead of being all spinulate. 



S:2.IItmeniacidon sulphurea, Bowerbank. 



Halichondiua sulphukea, Bean, MS. 



Sponge. Coating, surface smooth and even. Oscula and 

 pores inconspicuous. Dermal membrane pellucid, 

 abundantly spiculous. Spicula spinulate, large and 

 long, and very small, numerous, irregularly and thickly 

 matted together. Skeleton. Spicula spinulate, stouter 

 and shorter than (hose of the dermal membrane, very 

 numerous. 



Colour. Dried, sulphur-yellow. 



Locality. Scarborough, Mr. Bean ; Guernsey, Rev. A. 

 M. Norman. 



Examined. In the dried state. 



This sponge covers the surface of the sandstone on which 

 it is based for about two square inches, following its irre- 

 gularities, and in no part exceeding half a line in thickness 

 when dried. A few scattered orifices were apparent with a 

 half inch lens, probably oscula. When a portion of the 

 dermal membrane was viewed as a transparent object, with 



