162 notes on the kelp shell, Cantharidus irisodoiiles. 



The span of life of C. irisodontes appears to be about a year. Young shells first become visible 

 on the weed in January or February, but these have obviously been hatched several weeks previously. 

 Some localities are more forward than others. In March they are half grown, reaching a length of 

 4 mm. and numbering six whorls. By the end of April in Port Arthur the shell has attained its full 

 size, II mm., and has altered considerably in contour, the base having become narrower in proportion 

 to the length. By July and August the shell has been eroded or defaced by various incrustations ; 

 the earUer whorls, from which the animal has withdrawn, have also decayed and crumbled away. The 

 old shells disappear about October. 



The shells vary greatly in different localities. In some parts of Port Arthur they are solid, yet 

 in other beds scarcely a mile distant, they are so thin as to be not worth picking. Most of those from 

 Fortescue Bay are too thin to be used. Recherche Bay produces a long, narrow and unusually heavy 

 shell, which commands a high price. Shells of the finest lustre come from Black Jack, in the north 

 of the Tasman Peninsula. 



Shells are cleaned of animal matter by macerating them in water and allowing flies to work on 

 the decaying mass. If insufficiently cleaned, a black speck appears at the tip. The first process m 

 the manufacture of the necklaces is to grade the shells into sizes. 



The outer coat of the shell resists the penetration of dye. It may be removed by the agency of 

 lime or of acid. In the first case, chloride of lime is moistened with water till reduced to a thin paste. 

 In this the shells are mixed , the mass is well stirred and left to soak for several hours. The shells are 

 then removed, washed clean, and the under surface is found to be exposed in a glossv condition. 



When acid is employed, that material is economised, and the lustre of the shell improved, by 

 using it hot. To one gallon of boiling water three ounces of muriatic acid are added. The shells are 

 enclosed in a net bag, dipped and well shaken in the solution. Test the acid should eat too deeply, 

 the bag should be withdrawn from time to time and the contents examined. When the etching of the 

 acid has gone far enough, the bag full of shells is transferred to another vessel and thoroughly washed 

 in soap and water. This water must be tepid, for cold water would injure the nacre by cracking it. 



The shells are then strung. They are sold in their natural colour, or their appearance may be 

 varied by staining with aniline dyes of assorted shades. The dye is applied hot and in a net bag. 



A standard necklace is thirty-six inches long, with an average of eight shells to the inch, and a 

 weight of two ounces. When composed of the small shells, known to the trade as " gems," a neck- 

 lace may be as light as half-an-ounce. 



These Hobart necklaces not only supply the Australasian market, but are exported abroad. 



