47 



PLATE XIX. 



DICTYOCYLINDRUS STUPOsus, Bowerbank. 



Vol. ii, p, 116, ' Mon. Brit. Spongiadse.' 



Fig. 1. Represents a fully-developed specimen of 

 the species from Shetland iri the cabinet of the Rev. 

 A. M. Norman. The sponge had been dried, but 

 previous to being drawn it was immersed in water for 

 about twelve hours, which restored it to, as nearly as 

 possible, the condition in which it came from the sea, 

 Natural size. 



Fig. 2. A young specimen in the condition in which 

 it came from the sea at Shetland, having been preserved 

 in a saturated solution of salt in water. Natural size. 

 This specimen is attached by its natural base to a 

 pebble. 



Fig. 3. One of the large attenuato-acuate external 

 defensive spicula radiating from the surface of the 

 axial column of the sponge. X 80 linear. In the 

 living state these spicula project very slightly beyond 

 the dermal surface, but in dried specimens they are 

 frequently projected to the extent of half or two thirds 

 of their length in consequence of the contraction of 

 the abundant sarcode of the sponge. 



Fig. 4. Represents an average-sized, attenuato- 

 sphero-stellate, retentive spiculum from the dermal 

 membrane. X 530 linear. 



Fig. 5. One of the rather short cylindrical skeleton 

 spicula from the axial column. X 80 linear. 



Fig. 6. One of the slender acerate tension spicula 

 of the interstitial membranes. X 80 linear. 



Fig. 7. A slender acuate tension spiculum from 

 the interstitial membranes. X 80 linear. 



