344 



PLATE XCII. 



spiculum. X 250 linear that are occasionally found 

 mixed with the larger ones. 



IsoDiCTYA TUMULOSA, BotverhcinJc. 

 Plate XCII. 



Sponge. Massive, sessile, furnished with tumulous 

 cloaca3. Surface even or slightly rugose. Oscula 

 within the conical cloacas. Pores congregated ; porous 

 areas irregular, sparingly spiculous ; tension spicula 

 few in number, acuate, entirely spined, same size as 

 those of the skeleton ; retentive spicula bihamate 

 simple and contort and very minute simple bihamate ; 

 also bidentate equi-anchorate, large and small dermal 

 membrane pellucid, reticulated, rete irregular ; spicula 

 acuate, entirely spined, same size as those of the 

 skeleton. Skeleton. Primary lines multispiculate ; 

 secondary lines rarely more than bispiculous ; spicula 

 acuate, entirely spined, rather short and stout ; and 

 rarely spineless acerate with semi-hastate terminations. 

 Interstitial membranes sjjiculous, spicula same as those 

 of the dermal membranes, few in number. 



Colour. — Cream white. 



Habitat. — Torquay; J. S. Bowerbank. 



Examined. — In the wet and dried state. 



The form of this sponge is remarkable and very 

 characteristic, the whole of its upper surface is occu- 

 pied by four rudely conical tumulous elevations at the 

 summit of each of which there is a cloacal aperture ; 

 the surface of the sponge is more or less rugose or 

 papulous, and in the slightly depressed spaces the 

 porous areas are seated. The sponge was preserved 

 in a saturated solution of salt in water. In this state 

 when portions of it were examined microscopically the 

 sarcode was so abundant as to totally obscure its 

 structure, but in the dried state sections of it mounted 

 in Canada balsam at once revealed its true character. 



