348 PLATE XCII. 



abundantly spiculous ; spicula acuate, long and slender, 

 same size and form as those of the skeleton, dispersed 

 irregularly. Skeleton. Rather open and cavernous, 

 spicula acuate, long and slender, evenly diffused. 

 Sarcode abundant. 



Colour. In the dried state, light fawn brown. 



Habitat. Torquay; J. S. Bowerbank. 



Examined. In the dried state. 



I obtained this sponge at Torquay, and preserved it 

 in the condition it came from the sea in saturated salt 

 and water, small sections in this condition were per- 

 fectly impermeable to light, and its structure could not 

 be determined until the sections were mounted in 

 Canada balsam ; the abundance of sarcode totally 

 obscuring the vision. The dermal membrane is 

 pellucid and abundantly spiculous, the spicula being 

 dispersed as if thinly felted together on its surface, 

 and no difference exists in either size or form from 

 those of the skeleton tissues. A few small simple 

 oscula were visible on the surface of the sponge, but 

 the large orifices represented in the figure are the 

 mouths of numerous membranous tubes of annelids 

 that inhabited the sponge when alive, and which might 

 readily have been mistaken for oscula by a hasty 

 observation. The only species of Hymeniacidon with 

 which there is any probability of confounding this 

 species is H. caruncula and fallax. From the former 

 it would readily be distinguished by the difference of 

 its external characters, and the difference of the 

 spicula also readily distinguishes them, the skeleton 

 spicula of H. Aldousii, being longer and more slender 

 than those of H. caruncula, the length of the latter to 

 the former being as 7 to 10. The spicula of H.fallax, 

 are also less than those of H. Aldousii, being as about 4 

 to 5 in length, and also by being more or less fusi- 

 form in shape while those of H. Aldousii are purely 

 acuate, and no flexuous spicula are apparent. The 

 difference in their general aspect also greatly assists in 

 discriminating them. The simplicity of the structure 



