THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY, 



[TIHRD SERIES.] 

 No. 112. APRIL 1867. 



XXXVI. — Note on the Excavating Sponges ; with Descriptions 

 of four new Species. By Albany Hancock, F.L.S. 



[Plates VII. & VIII.] 



Since the publication of my paper on the excavating Sponges*, 

 I have reexamined nearly all the species therein described, and 

 have carefully investigated several new and interesting forms 

 from various parts of the world ; and, as a result of these re- 

 searches, 1 have ouly become more confirmed in the opinion 

 that these lowly organized creatures are endowed with the power 

 (of whatever nature it may be) of forming in shell and other 

 hard calcareous bodies the crypts and channels within which 

 they lie concealed. The means by which this work is achieved 

 is still, I frankly admit, involved in much obscurity. 



Shortly after the appearance of the paper above alluded to, I 

 satisfied myself that the larger bodies found in contact with the 

 surface of Cliona celata were not organically connected with it, 

 as I originally thought, but were really nothing more than 

 decalcified portions of the horny membranous tissue of the 

 oyster-shell within which the Cliona was buried; and some time 

 ago I wrote to Dr. Bowerbank to this effect f. If, therefore, 

 Cliona works out the cavities it inhabits in the manner I sup- 

 posed, namely, mechanically, it must be by the aid of the smaller 

 bodies described in my paper, or by the spicula themselves. 



My object, however, on the present occasion is not to discuss 

 the means by which Cliona excavates its habitation, but rather 

 to give some additional specific characters that distinguish the 

 British species, and which originally escaped observation. But 

 in the first place it must be stated that Dr. Bowerbank is not 

 exactly correct when he asserts, as he has done in the second 



* Ann. & Mag. Nat. Hist. ser. 2. vol. iii. p. 321, May 1849. 

 t Ou the 28th of Febniary, 1866. 



Ann. &; Mag, N, Hint, Scr.3. Vol.xix. 17 



