324 PLATE XC. 



the terminations of the skeleton fibres on the inner 

 surface of the dermis. X 36 linear. 



Fio\ 11. One of the skeleton spicula. X 250 



linear. 



Fig. 12. One of the large bihamate retentive spicula 

 from the dermal membrane. X 530 linear. 



Fio-. 13. A bideutate, inequi-anchorate, retentive 

 spiculum from the dermal membrane. X 530 linear. 



Fig. 14. One of the dentate-palmate, inequi-anchorate 

 retentive spicula from the dermal membrane. X 530 

 linear. 



RAPHIODESMA SIMPLISSIMA, Bowerbanh. 

 Plate XC. 



Sponge compressed, thin, fan-shaped, sessile. Sur- 

 face smooth and even. Oscula simple, minute. Pores 

 inconspicuous. Dermal membrane abundantly spicu- 

 lous ; spicula acuate, long and slender, closely fitted 

 together. Skeleton. Fasciculi multispiculous, variable 

 in size and length, disposed irregularly; spicula 

 acuate, long and stout; bases and apices of each 

 fasciculus coincident. Interstitial membranes. Spicula 

 same as those of the dermis, few in number. 



Colour. In the dried state, light brown. 



Habitat. Isle of Mull ; Rev. A. M. Norman. 



Examined. In the dried state. 



I received a single specimen of this sponge from 

 Mr. Norman in the spring of 1873. It is half an inch 

 in height, one and a quarter in breadth, and it does 

 not exceed a line in thickness. It has a torn base, 

 but has every appearance of having been sessile. The 

 spicula of the dermal membrane are nearly as long as 

 those of the skeleton ; they are purely acuate, variable 

 in size, and the largest of them are frequently flexuous. 

 Their mode of disposition is usually irregularly felted 

 together, but sometimes they are parallel to each 

 other, forming irregular patches, and occasionally they 

 are more or less fasciculated. The skeleton fasciculi 



