147 



PLATE LVIII. 



ISODICTYA BEANII, Hoiverbank. 



Vol. ii, p. 334, ' Mon. Brit. Spongiadffi.' 



Fig. 1. Represents the specimen I received from 

 Mr. Bean. Natural size. 



Fig. 2. A slender, attenuato-acuate, tension spicu- 

 lum from the dermal membrane. X 250 linear. 



Fig. 3. One of the slender, tricurvate, tension 

 spicula from the dermal membrane. X 530 linear. 



Fig. 4. A minute, equi-anchorate, retentive 

 spiculum from the dermal membrane. X 530 linear. 



Fig. 5. One of the subfusiformi-acuate skeleton 

 spicula from the primary lines. X 250 linear. 



Fig. 6. One of the acuate, entirely spined, short, 

 skeleton spicula from the secondary lines of the 

 skeleton. X 250 linear. 



ISODICTYA FIMBEIATA, Bowerbank. 



Vol. ii, p. 337, ' Mon. Brit. Spongiadae.' 



Figs. 7, 8, 9, 10. Represent specimens of the 

 sponge, for which I am indebted to my friend the Rev. 

 A. M. Norman, who dredged them at Shetland. 

 Natural size. No. 8 is based on the remains of a small 

 bivalve shell. 



Fig. 11. An acuate tension spiculum from the 

 dermal membrane. X 250 linear. 



Fig. 12. One of the large, tridentate, bifimbriated, 

 equi-anchorate, retentive spicula from the dermal 

 membrane. X 530 linear. The fimbriation of these 



