14t) TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



XVIII. 



A CURIOUS DWELLING FOR A HERMIT- 

 CRAB. 



BY THOMAS SCOTT. 



With one Plate. [I.] 

 [Read 31st March, 1885.] 



On the 7tli of February last, my friend Mr. John 

 Murray, Greenock, brought me a rather curious 

 marine object which had been got in Gourock Bay. 

 It had an irregular, rounded form, and was rather 

 firm in texture, its diameter being about \\ inch, 

 and its colour dusky. In size and colour it very 

 much resembled a small tuber, and has been called 

 by some friends a "sea potato." There was an open- 

 ing in the side of this "sea potato" of a somewhat 

 regular outline, which formed the entrance to a 

 cavity penetrating deep into its substance {fi^. 1). 

 Just visible within the cavity we could see what 

 looked like the claws of a crab, merely the tips 

 being shown. In fact, it was rather puzzhng at first 

 sight to make out what the object could be. 



As soon as I had a little leisure I bisected the 

 " potato " through the middle of the opening referred 

 to, as nearly as possible in the plane of the curve of 

 the cavity; and the true nature of the object then 

 became apparent. It proved to be a sponge ; and on 

 boiling a little of its substance in a dilute solution 

 of caustic potash, an immense number of slightly- 

 bent needle-shaped spicules were obtained, the 

 spicules being all of this form. It thus agreed fairly 

 well with the genus Hyjneniacidon, described by Mi-. 

 Philip Henry Gosse in A Year by the Shore. I also 

 found that the cavity referred to took a spiral form, 

 with the turns nearly in the same plane (fig. 2), and 



