THE MAGILUS. 



379 



Many other molluscs secrete a coloring fluid, such as Murex trunculiis, which was 

 another of the shells employed to furnish the imperial purple ; and Murex brandaris 

 seems to have been used for a similar purpose. One of the staircase shells, Scalaria 

 diadema, also secretes a purple-producing substance ; and Cerithium telescopium has 

 been known to stain a piece of paper a permanent green. 



MAQlLVS.-Mmgllus aatlquus. 



ONE of the strangest, though not the most beautiful, of shells is the MAGILUS, a 

 native of the Red Sea and the Mauritius. 



On reference to the illustration, the reader will see two figures, one representing a 

 group of madrepores, in which a small and delicate shell is lying, and the other a 

 long, crumpled, and partly spiral tube, with a shell at one end and an opening at the 

 other. Strange as the assertion may seem, these two figures represent the same animal 

 in two stages of its development. 



For the purpose, apparently, of carrying out some mysterious object, the Magilus 

 resides wholly in the masses of madrepore, and in its early youth is a thin and delicate 

 shell without anything remarkable about it. As it advances in age, it enlarges in size, 

 as is the case with most creatures ; but its growth is confined to one direction, and, 

 instead of enlarging in diameter, it merely increases in length. The cause of the 

 continual addition made to its length is probably to be found in the growth of the 

 madrepore in which it is sheltered, and which would soon inclose the Magilus within 

 its stony walls did not the mollusc provide against such a fate by lengthening its shell 

 and taking up its residence in the mouth. 



The most curious point, however, in the economy of the Magilus is, that, as fast as it 

 adds a new shell in front, it fills up the cavity behind with a solid concretion of shelly 

 matter, very hard, and of an almost crystalline structure, so as to leave about the same 

 amount of space as in the original shell. The animal is always to be found in the 

 very front of the shelly tube, and closes the aperture with a strong operculum that 

 effectually shields it against all foes. 



The color of the Magilus is whitish. Only one species is known. 



In the peculiar formation of the shell there is an evident analogy with the successive 

 chambers formed by the pearly nautilus. In both cases the animal is of small dimen- 



