PLATE X. 



IsoraoTTA iNVOLUTA, BowerhanTc. 



Fig. 1. — The type growing on Nullipara polymorpha. 

 From "Westport Bay. In the collection of the Rev. 

 A. M. Norman. 



Fig. 2. — A portion of the dermal membrane. 



Fig. 3. — One of the slender, acuate, tension spicula. 



Fig. 4. — One of the stout acuate spicula of the 

 skeleton. 



IsoDicTYA PAUPBRCULA, Bowerbank. 



Fig. 5. — The type on the inside of a valve of Pecten 

 varius. From Birterbuy Bay. In the cabinet of 

 the Rev. A. M. Norman. 



Fig. 6. — A portion of the sparingly spiculous dermal 

 membrane. 



Fig. 7. — Very slender aoerate spicule of the dermal 

 membrane. 



Fig. 8. — One of the stout acerate spicula of the* 

 skeleton. 



[Fig. 9. — This Plate was engraved before Dr. Bower- 

 bank's death, but not lettered ; nor was any descrip- 

 tion of it to be found among the author's papers. 

 The bidentate equi-anchorate spicula (Fig. 9) is of 

 very unusual form, but no sijch spicule is referred to 

 in the descriptions of the two sponges which are 

 illustrated in this Plate.] 



