340 PLATE XCL 



Halichondria MoIntoshii, Bowerbank. 

 PLATE XCI. 



Sponge : coating thin. Surface smooth and even. 

 Oscula more or less elevated, dispersed. Margins 

 thin. Pores inconspicuous. Dei-mal membrane 

 aspiculous. Skeleton. — Very irregular ; rete mostly 

 unispiculous, occasionally bi- or trispiculous ; spicula 

 acerate, short, and stout. Interstitial membranes 

 aspiculous. 



Colour. — In the dried state, light nut-brown. 



Habitat. — St. Andrew's, Scotland ; Dr. Mcintosh. 



Examined. — In the living and dried state. 



I received seven specimens of this species from 

 Dr. Mcintosh, four of them were wet from the sea. 

 In his note accompanying the wet specimens he 

 states, "It is not uncommon at St. Andrew's on the 

 under surface of stones in littoral pools ; the specimens 

 sent covered an area of about eight or nine inches. 

 It is of a dull grey colour." In the dried state the 

 colour is light or greyish nut-brown. 



The greatest part of the specimens did not exceed 

 the eighth of an inch in thickness, but a jDortion of 

 one small specimen, an inch in diameter, was nearly a 

 quarter of an inch thick for about half its area, the 

 whole of its surface was much more irregular than 

 those of the other specimens. All of them had 

 evidently been closely adherent to a solid surface. 

 The dermal membrane in the specimen fresh from the 

 sea was in an excellent state of preservation. It was 

 pellucid and closely adherent to the surface of the 

 skeleton beneath, but there was not the slightest indi- 

 cation of any spicula peculiar to that organ. The 

 characters of the oscula varied considerably on the 

 different specimens in regard to their elevation. In 

 some of them they were scarcely raised above the 

 dermal surface, those on the specimen figured exhibit 

 the greatest amount of development observed. I 



