THE MAGILUS ANT1QUUS. 



291 



Murex haustellum. 



When the sea is quiet, these little creatures, 



Like li Ltle wanton boys that swim on bladders, 



appear in vast shoals on the surface, but as soon as the 

 wind ruffles the ocean, or an enemy approaches, they at 

 once empty their air-cells, contract their float, and sink to 

 the bottom, pouring out at the same time a darkened fluid 

 like that of the Aplysia or the Murex, which no doubt 

 serves them as a defence against 

 their foes, and, according to Lesson, 

 furnished the celebrated purple of 

 the ancients. The Ianthinse inhabit 

 the Mediterranean and the warmer 

 regions of the Atlantic, but especially towards the close of 

 summer they are frequently drifted by the Gulf Stream to the 

 west coast of Ireland. 



While the vast majority of the gasteropods either creep or 

 swim, some are doomed to the sedentary life of the oyster, 

 and remain for ever fixed to the, spot where 

 they first attached themselves as small free- 

 swimming larvae. Thus the Magilus an- 

 tiquus, which in its young state presents all 

 the characters of a regular spiral univalve, esta- 

 blishes itself in the excavations of madrepores, 

 and as the coral increases around it, the Magilus 

 is obliged, in order to have its aperture on a 

 level with the surrounding surface, to construct 

 a tube, lengthening with the growth of the 

 coral. As the tube goes on increasing, the 

 animal abandons the spiral for the tubular part of the shell, and 

 in the operation it leaves behind no partitions, 

 but secretes a compact calcareous matter which 

 reaches to the very summit of the spiral part, so 

 that in an old specimen the posterior part of the 

 shell presents a solid mass. 



The Siliquarise are generally found embedded 

 in a similar manner in sponges or other soft 

 bodies, while the Vermetus, or Worm-Shell, usually 

 attaches itself, like the Serpulae, to rocks, coral-reefs, 

 shells. 



Magilus antiquus. 



Worm-Shell. 



or 



