246 PLATE liXXIX. 



Hymebaphia coeonula, Bowerhank. 

 Plate LXXIX. 



Sponge. Coating, thin. Surface uneven, both strongly 

 and minutely liispid. Oscula simple, dispersed ; pores 

 inconspicuous. Dermal membrane spiculous ; tension 

 spicula acerate, very long and slender, flexuous, dis- 

 persed singly or fasciculated, fasciculi frequently poly- 

 spiculous ; external defensive spicula, the larger arising 

 from the projection of the distal extremities of the 

 skeleton spicula through the dermal membrane ; the 

 smaller ones attenuato-spinulate, entirely-spined, basal 

 bulb often coronulated spinuously. Skeleton : spicula 

 spinulate, very long and large, distal end usually joro- 

 jected through the dermal membrane. Basal mem- 

 brane pellucid : tension spicula same as those of the 

 dermis, dispersed singly, few in number ; internal 

 defensive spicula same as those of the dermal mem- 

 brane ; sarcode abundant. 



Colour. — Dried, light grey. 



Habitat. — Shetland, Rev. A. M. Norman. 



Ecvamined. — In the dried state. 



The sponge covers about one third of the outer 

 surface of a small bivalve shell. The surface of the 

 sponge is very irregular, and has numerous extraneous 

 matters incorporated in it. The hispidation, when 

 viewed as an opaque object, is seen to be produced to 

 a great extent by the projection of the large skeleton 

 spicula through the dermis, frequently to the extent of 

 more than half their length ; the smaller or secondarjr 

 hispidation is effected by the small attenuato-spinulate, 

 entirely-spined, defensive spicula, the bulbs of which 

 are within the dermal membrane, and the shafts only 

 appear externally ; so that when we view the internal 

 surface of the dermal membrane in Canada balsam, 

 witli a power of about 300 linear, we observe two sets 

 of these defensive spicula ; one having their shafts 

 projecting from the basal membrane inward towards 



