326 PLATE XC. 



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

 Archer. Liverpool Museum. 



Exariiined. — In tlie dried state. 



Among a series of specimens of s^^onges from the 

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

 curator for examination, there v?as 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 be an Isodictya which I could not refer to any 

 known British species. When examined hj 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 scai-cely visible without the assistance 

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

 dermis mo anted in Canada balsam, detect the pores. 

 The dermal membrane is very pellucid, and abundantljr 

 furnished with spicula of the same form and size as 

 those of the skeleton ; from whicli they can scarcely 

 be separate]}' distinguished in sit/I, iu a portion of the 

 dermis mounted in Canada balsam. The bidentate, 

 equi-anchorate, I'etentive spicula are exceedingly few 

 in lunnber, and arc very minute, requiring a power of 

 seven or eight liundred linear to render them distinctly 

 to tlic 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 tlie secondary 

 ones ; a few of them are multispiculous. Tlie primai'y 



