OF THE SPONGIAD.E. 261 



FIG. 



form previously described ; and although inter- 

 mingled with them and the other forms of 

 spicula in Euplectetta aspergittum, Owen, it is 

 always readily to be distinguished by an expe- 

 rienced observer. 



The spines are small but thickly dispersed over 

 the apices of the radii for a short way down the shaft, 

 and occasionally the apices of the radii are more or 

 less clavate. 



. CYLINDRO-RECTANGULATED TRIRADIATE. This form 

 of spiculum is abundant in Dactylocalyx pumicea, 

 Stutchbury. The basal axial ray is often very 

 much elongated. The radii are also incipiently 

 spined, and their apices are more or less spinulate 

 or clavate. The form of this spiculum is precisely 

 that of Fig. 198, excepting that the radii are 

 cylindrical instead of attenuated. 



199. SPICULATED BITERNATE. X 90 linear. I found 



several of these spicula in the dust shaken from the 

 siliceo-fibrous massive sponge Farrea occa, Bower- 

 bank, MS., at the base of my friend Dr. A. Farre's 

 specimen of Euplectella cucumer, Owen, and I have 

 no doubt of their belonging to the sarcode of the 

 sponge at its base. They appear to vary greatly 

 in the amount of their development. In Fig. 199 

 the biternate spicula are simple, and it is spicu- 

 lated at one end only. Some of them were similar 

 to Fig. 199, but were spiculated at both ends. 



200. FURCATED SPICULATED BITERNATE. X 130 linear. 



From Farrea occa, Bowerbank, MS. These spicula 

 are intermixed with those represented by Fig. 199. 

 They vary considerably in size, and in the number 

 of the rays which are furcated. 



