146 BRITISH SPONGES: 



that the calcareous particles must have been extrinsic and foreign 

 to the sponge. 



The figure of H. Ficus is liable to some modification from 

 the nature of the object it grows upon. If this has an even 

 broad surface, like a bivalve shell, the sponge fixes itself with a 

 spreading crustaceous base and rises up on a thick strong neck ; 

 but if the shell is univalve and cylindrical, then the base of the 

 sponge is limited, and the neck slender and pedicellate, sup- 

 porting a heavy bulbous head, such as it is represented by Es- 

 per, of whose figure I have given a copy at page 77. Esper's 

 specimen grew from a Turritella, and Mr Hogg found the 

 sponge assuming precisely the same form when it had attached 

 itself to the Dentalium. 



H. Ficus has no relation to the Alcyonium Ficus of Pallas, 

 or Alcyon. pxdmonavia of Ellis, which is one of the compound 

 tunicated MoUusca. 



34. H. CARNOSA, Jig-shajyed, compact andjleshy, the sur- 

 face smooth and even ; interior yelloicish ; sjncida ivith a bul- 

 bous head, tapered to a sharp point. 



Plate XIII, Fig. 7, 8. 



JIab. Roundstone bay, Cunnamara, 3Ir Wm. M'CoNa. 



Sponge irregularly ovate, as large as a plum, fleshy and very 

 compact, of an olivaceous colour after being preserved in spirits, 

 the surface even and very smooth, unporous, and with only one 

 or two imperfectly formed oscula on the sides. The interior is 

 solid, fleshy and homogeneous, tinted with yellow, and permeat- 

 ed with slender sinuous canals, which do not penetrate the thin 

 skin. The spicula are minute and lie principally in parallel fas- 

 cicles in the animal matrix : they are pretty imiform in size and 

 form, and, when entire, have a bulbous head like a pin, whence 



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