326 PLATE XO. 



Habitat. Clew Bay, July, 1872; Mr. Samuel 

 Archer. Liverpool Museum. 



Examined. In the dried state. 



Among a series of specimens of sponges from the 

 Liverpool Museum sent to me by Mr. T. J. Moore, the 

 curator for examination, there was an unsightly mass of 

 a large dried ascidian attached to an old valve of, ap- 

 parently, a cardita, covered by minute vegetables, 

 zoophytes, and other matters, and amidst them irre- 

 gular patches of a soft light grey sponge closely 

 adherent to the ascidian. They do not present a 

 regular even surface, but each patch assumes the 

 appearance of several small sessile nodulous sponges 

 united by approximation. On examining microscopi- 

 cally a portion of one of those little masses I found it 

 to l3e an Isodictya which I could not refer to any 

 known British species. "When examined by the aid of 

 a lens of about two inches focus, the surface presents 

 a somewhat asperated appearance. This is pro- 

 duced by the occasional protrusion of the terminations 

 of the primary lines of the skeleton at various 

 angles. 



The oscula are scarcely visible without the assistance 

 of a lens, and I could not, even in a portion of the 

 dermis mounted in Canada balsam, detect the pores. 

 The dermal membrane is very pellucid, and abundantly 

 furnished with spicula of the same form and size as 

 those of the skeleton ; from which they can scarcely 

 be separately distinguished in situ, in a portion of the 

 dermis mounted in Canada balsam. The bidentate, 

 equi-anchorate, retentive spicula are exceedingly few 

 in number, and are very minute, requiring a power of 

 seven or eight hundred linear to render them distinctly 

 to the eye. 



The skeleton structures are very diffuse and irre- 

 gular in the mode of their disposition. The primary 

 lines are always more or less multispiculous ; and there 

 is no regularity in the spaces between the secondary 

 ones ; a few of them are multispiculous. The primary 



