492 Zoological Illustrations : — Spongia suheria, 



with a thick somewhat inflected and plaited rim. Where the 

 sponge incrusts the shell it is thin, but the tubular processes 

 are between two and three lines in diameter, and, when re- 

 moved at the base, they leave a mark exhibiting a circle of 

 cells radiating to the outer edge. 



I am of opinion that this is the 5p6ngia suberia of Mon- 

 tagu {Wern. Mem., i. 100.), in a perfect state. Montagu 

 seems to have met with specimens only previous to their pro- 

 duction of the tubular processes, and, if we subtract these 

 from our description, it will be found to correspond in other 

 respects with the description of this excellent observer. He 

 says that the " sponge is of a corky nature, resembling the 

 close texture of the stalk of some species of jBoletus. It 

 has rarely any other pores than what are formed by the fibres, 

 which are so extremely fine, as not to be visible to the naked 

 eye, even when broken ; and with the assistance of a pocket 

 lens, they are not definable on the surface. Its colour is 

 orange-yellow when fresh, becoming brown when dry : its 

 shape is indefinite, but it has the singular property of being 

 attached only (as far as I have been able to ascertain) to old 

 univalve shells, which it entirely invests. It is also remark- 

 able, that few instances occur where the hermit crab has not 

 formed a lodgement in the nucleus shell, and there appears 

 to be a great struggle between the two parasitical intruders, 

 as the sponge is continually endeavouring to fill up the aper- 

 ture of the shell, while the crab, by its occasional motion in 

 search of prey, frustrates that natural propensity of the sponge. 

 Notwithstanding the efforts of so active and restless an in- 

 truder, the gradual and insensible increase of the sponge gains 

 upon the premises of the crab ; it pushes it on all sides, and 

 completely lines the interior surface of the shell, so that the 

 crab soon finds its habitation too small, and is compelled to 

 search for a more capacious house." 



Dr. Fleming has placed this sponge in his genus Halichon- 

 dra (Brit, Anim,, p. 522.), distinguished from the other 

 genera of the family by the siliceous spicula which enter so 

 abundantly into its organisation ; and he says that the spicula 

 of the species in question, which he has found " incrusting 

 corallines in the Frith of Forth," are fusiform and slightly 

 curved. Montagu makes no mention of these spicula, which 

 probably require a high power of the microscope for their 

 detection, and hence they also escaped my observation. To 

 any correspondent of this Magazine I should feel much in- 

 debted by the communication of specimens of the 5p6ngia 

 suberia, either dried or preserved in spirits. 



Berwick upon Tweed, June 12. 1834. 



