21 



PLATE XLVIII. 



IsoDiOTYA ciNEREA, BoiDerbank. 



Vol. ii, p. 274, ' Mon. Brit. Spongiadffi.' 



Fig. i. — Represents a specimen of tlie species in a 

 fine state of preservation from Fowey, Cornwall, by 

 Mr. C. W. Peacli. Natural size. 



Fig. 2. — One of the type-specimens of the species 

 in the Johnstonian collection in the British Museum 

 marked 17". Natural size. 



Fig. 3. — Another specimen of the species in the 

 Johnstonian collection in the British Museum marked 

 17''. Natural size. 



Fig. 4. — A skeleton spicvilum, from the specimen 

 represented by fig. 2. X 250 linear. 



Fig. 5. — One of the tension spicula, from the inter- 

 stitial membranes of the specimen represented by fig. 2. 

 X 250 linear. 



I regret that I have been unable to figure the type- 

 specimen of this sponge. I applied to my friend 

 Professor Grant for the loan of it for that j^urpose, 

 but unfortunately, although diligently searched for, it 

 could not be found. When I wrote the description of 

 this sponge, in vol. ii, p. 275, of the ' Mon. Brit. 

 Spongiadse,' I believed it to be a rare species, but 

 since that time I have obtained numerous specimens 

 from various localities exhibiting considerable varia- 

 tions in form. Very few of them exceeded the figiu^ed 

 specimen, Plate XXXVII, fig. 1, in size; but since 

 then I have examined a spechnen I obtained from the 

 Diamond Ground off Hastings that greatly exceeds any 

 of those previously acquired in its dimensions, and 

 which, unlike any of them, appears to have risen from 

 a sessile base and to have assumed a rudely compressed 

 fan-like form, two and three quarters inches high and 



