36 PLATE XIV. 



Fig. 6. — One of the skeleton spicula. X 80 linear. 



In vol. i, plate xxxi, fig. 362 represents a section at 

 right angles to the surface of a specimen of T. cranium, 

 exhibiting the radiating defensive fasciculi of spicula and 

 other interesting points in the anatomy of the sponge. 



In the same volume, plate xxv, fig. 343 represents 

 the two sorts of gemmules that are found in adult 

 specimens of T. cranium, and fig. 344 a gemmule of 

 the largest description in its natural state, as seen by 

 direct lio-ht. X 25 linear. 



In the same volume, plate iv, figs. 77 to 82, the 

 poiTecto-ternate and recurvo-ternate defensive spicula 

 are represented and described. 



This sponge is subject to much variation in size in 

 different localities. 



Mr. Barlee sent me twelve specimens in the dried 

 state, which he dredged at the Isle of Arran, Galway. 

 None of them exceeded the size of a large di'ied pea. 

 On making a vertical section of one of them I found all 

 the characteristic spicula of the species, but not so fully 

 developed as in the larger specimens from Shetland. 



