110 A MONOGRAPH OF THE 



the sponge had attained about its greatest altitude. In 

 height and general habit it may readily be mistaken for 

 Halichondria Hyndmanii, but the branches do not ter- 

 minate in a corymbose manner, as in that species. In the 

 dry condition the projection of the surface spicula is nearly 

 equal to the diameter of the primary branches. In the 

 dried state the surface is irregularly and deeply excavated, 

 but it is probable that this character would not be apparent 

 in the living sponge. 



The spicula of the skeleton are somewhat irregular in 

 structure ; the normal form is regularly acuate and flexuous, 

 but occasionally they are sub-spinulate or sub-cylindrical ; 

 the distal termination is usually gradual and regular, but 

 sometimes it is much attenuated and at others abrupt, and 

 in the latter case it is often more or less mucronate. The 

 internal defensive spicula are very few in number, and are 

 not to be readily found, either in situ or after the separation 

 of the spicula in boiling nitric acid ; occasionally they are 

 subspinulate. 



The opaque gemraular bodies are dispersed irregularly 

 amidst the tissues, sometimes appearing attached to the 

 spicula, but more frequently slightly imbedded in the sur- 

 face of the interstitial membranes ; they have the appear- 

 ance of a transparent- integument, comparatively thick, 

 enclosing an opaque, dark, steel-gray coloured nucleus. I 

 could not discover any indication of spicula belonging to 

 the integument, either in situ or after treatment with 

 boiling nitric acid. 



7. DiOTiocYLiNDRUS FASCicvLARis, Bowerbank. 



Sponge. Arborescent, slender; branches cylindrical, di- 

 viding dichotomously. Surface smooth, aspiculous. 

 Oscula and pores inconspicuous. Dermal membrane 

 simple, translucent, aspiculous. Skeleton. Dense, 

 abundantly spiculous ; spicula attenuato-acuate, slen- 

 der, often flexuous ; furnished with distinct radiating 

 fasciculi of external defensive spicula ; spicula of the 



