248 PLATE LXXIX. 



corona of spines of many of them embedded in the 

 sarcode of the inner surface of the membrane 

 while their shafts were projected from its outer sur- 

 face, there has always been such an accumulation 

 of semi- opaque sarcode around them as to prevent 

 a clear and satisfactory view of their embedment 

 and structure. The peculiarities of their spination 

 would seem to favour the idea I have enunciated ; the 

 circlet of spines would assist in retaining them in their 

 positions, while the smooth space between the circlet 

 of spines and the commencement of the spination of the 

 shaft would allow not only of their closer envelopment 

 by the surrounding membrane, but also of a certain 

 amount of free motion to provide against external 

 contingencies. 



HTMEDESMIA INFLATA, Bowerbank. 

 Plate LXXIX. 



Sponge. Coating, thin. Surface even, smooth. 

 Oscula simple, small. Pores inconspicuous. Dermal 

 membrane, abundantly spiculous ; spicula acerate, pro- 

 fusely spinous ; frequently angulated, inflato-acerate ; 

 spines irregularly dispersed, acute, exceedingly nu- 

 merous. Skeleton fasciculi. Spicula acerate, slender, 

 numerous and closely packed; occasionally large and 

 long, and rarely, with a central inflation, dispersed ; 

 and also very large and long, spinulate or rarely acuate 

 spicula irregularly dispersed, and always prostrate be- 

 neath the dermal membrane. Internal defensive spicula. 

 Attenuato-spinulate, entirely andprofusely spinous, short 

 and stout, spinulate base largely developed; spines acute, 

 frequently recurved ; spicula very few in number. 



Colour. Light brown in the dried state. 



Habitat. Shetland, Mr. W. C. Peach. 



Examined. In the dried state. 



I found three specimens of this species among a 

 considerable number of small pebbles from Shetland, 

 having thin patches of Hymeraphi as and Hymedesmias 



