314 PLATE LXXXIX. 



IsOOrCTYA INGEETA, BoiOiirljOMlu. 



Plate LXXXIX. 



Sponge sessile, more or less fan-sliaped. Surface 

 smooth and even. Oscula simple, minute, dispersed. 

 Pores inconspicuous. Dermal membrane abundantly 

 spiculous ; spicula irregularly reticulated ; rete uni- 

 spiculate, occasionally fasciculated, same form and size 

 as those of the skeleton. Skeleton very diffuse and 

 irregvilar ; primary lines multispiculous ; secondary 

 lines mostly luiispiculous, numerous and very irregular ; 

 spicula acerate, rather largo. 



Colour. — In the dried state, milk white. 



ILiJAtat.—Me oi'MnW. Rev. A. M. Norman. 



j'l.ranunecl. — In the dried state. 



1 received four of these little sponges for exami- 

 nation from Mr. Norman ; the whole of them were of a 

 compressed or fan-shaped form, and of thickness of 

 about two or three lines, the figured one being the 

 lartrest of the four. The l)asal attachment in all the 

 specimens was at one edge of the thin piate of sponge, 

 and both the broad surfaces were evidently inhalent 

 ones. Very few of the oscula were visible, and those 

 were very minute. The pores were not visible to the 

 unassisted eye, but in portions of the dermis mounted 

 in Canada balsam they were seen to be numerous, Imt 

 rarely more than one in any of the areas of the dermal 

 reticulations. 



'JMie reticulations of the skeleton are Avide and very 

 irregular. The primary lines are nuiltispiculous, and 

 the secondary series are so irregular and numerous 

 that its structure is not readily determined unless 

 under favorable circumstances, iu a section cai^efully 

 cut at right angles to the surface. There is no appre- 

 ciable diil'erence in the size and form of the spicula of 

 the skeleton and those of the dermal membrane, and no 

 other form could be detected in any part of the sponge. 



The only s])ecies of known British Isodictya with 



