288 PLATE LXXXV. 



the latter the spicula closely resemljle those of /. fila- 

 menta, but the open arrangement of the rote of the 

 skeleton and the hispid surface of the sponge will 

 readily distinguish it from the species under de- 

 scription. 



IsoDiCTYA LUTEOSA, Bowerhank. 

 Plate LXXXV. 



Sponge parasitical on small fuci. Surface smooth, 

 but somewhat corrugated. Oscula simple, dispersed. 

 Pores inconspicuous. Dermal membrane aspiculous, 

 abundantly minutely granulated ; granules pellucid, 

 evenly and very closely disposed. Skeleton. Very 

 irregular ; primary lines multispiculous, tortuous ; 

 secondary lines very irregularly disposed ; varying 

 from unispiculous to multispiculous. Spicula acerate, 

 small and short. Interstitial membranes sparingly 

 spiculous ; spicula of the same form as those of the 

 skeleton, but shorter and more delicate in form. 



Golour. — Slate-grey or mud colour. 



Habitat. — Portaferry, Strangford Lough ; Rev. A. 

 M. ISTorman. 



Examined. — In the dried state. 



This is certainljr the most unprepossessing sponge 

 that I have ever examined. In its external character 

 it very closely resembles an elongate mass of the 

 fibrous stems of a small fucus cemented together by 

 dried mud. 



Although thus repulsive in its outward appearance, 

 its internal structures are in an excellent state of pre- 

 servation, but in a most puzzling condition for ex- 

 amination. At the first view, with a low power, at a 

 thin slice mounted in Canada balsam, it has much of 

 the aspect of a very iri'egidar Hymeniacidon, but a 

 closer acquaintance with its skeleton with higher 

 powers reveals unmistakably its character as an 

 Isodictya. 



The primary lines of the skeleton near the dermal 



