288 PLATE LXXXV. 



the latter the spicula closely resemble those of I. fila- 

 menta, but the open arrangement of the rete of the 

 skeleton and the hispid surface, of the sponge will 

 readily distinguish it from the species under de- 

 scription. 



ISODIOTYA LUTEOSA, Bowevbank. 

 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. 



Colour. Slate-grey or mud colour. 



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

 M. Norman. 



Examined. In the dried state. 



This is certainly 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 irregular 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 



