Conchology. 1 03 



The solution of the unburnt shell was also similaT, excepting 

 only that the gelatinous part was of a greater consistency. 

 When the river muscle was burnt in a crucible, it emitted 

 much smoke, with a strong smell of burnt horn or cartilage ; 

 the shell became of a dark gray color, and exfoliated. By 

 solution in the acids, the proportion of carbonic matter sep- 

 arated was greater, and that of carbonate of lime obtained 

 was less, than from the other shells on which experiments 

 were made. 



When an unburnt shell of this description was immersed 

 in diluted nitric acid, a rapid solution and eft'ervescence took 

 place, and, at the end of two days, the whole of the carbon- 

 ate of lime was nearly dissolved. A series of membranes now 

 only remained, of which the epidermis constituted the first. 

 These membranes still retained the figure of the shell. The 

 carbonate of lime was at first readily dissolved, because the 

 acid came easily in contact with it ; but the process became 

 slower as it was more difficult for the acid to insinuate itself 

 between the different membranes of which the shell is com- 

 posed. The Haliotis iris, and the Turbo olearius, were found 

 to resemble this muscle, except that the membranaceous parts 

 were more compact and dense. 



When these shells are deprived, by an acid, of the carbon- 

 ate of lime, which gives them their hardness, they appear to 

 be formed of different membranes, applied stratum super stra- 

 tum. Each membrane is furnished with a corresponding coat 

 or crust of carbonate of lime, and it is so situated, that it is 

 always between every two membranes, beginning with the 

 epidermis, and ending with the internal membrane, which has 

 been last formed. The animals which inhabit these stratified 

 shells, increase their habitation by the addition of a stratum 

 of carbonate of lime, which is secured by a new membrane. 

 And, as every additional stratum exceeds in extent that which 

 was previously formed, the shell becomes stronger in propor- 

 tion as it is enlarged ; and thus the growth and age of the 

 animal may be denoted by the number of strata of which the 

 shell is composed. Similar experiments were made on spe- 

 cies of mother of pearl, as they are imported from China, and 

 with precisely the same results. They appeared to be com- 

 posed of the same gelatinous matter, and carbonate of lime. 

 In all the shells of this description which were immersed in 

 acids, the membranaceous parts retained the exact figure of 

 the shell, and they appeared distinctly to be composed of 

 fibres, arranged in a parallel direction, corresponding to the 

 configuration of the shell. 



