INTRODUCTION. XUl 



that of other shells, it is not surprising that we find 

 proofs of the formation of the regular projections, 

 which the extremities of the layers leave by the 

 side of each other. The colours of the mould are 

 different from those of the exterior layers, and it 

 frequently shows the transversal bands with which 

 it is marked, while the enamel is adorned with 

 spots or stains, because some parts of the body are 

 supposed to furnish this composition, which is se- 

 creted from certain moist glands, of a different kind 

 from those of the wings. 



Thus we remark two distinct operations in the 

 formation of the cowry. The first is that which 

 produces the part of the shell called the mould, and 

 is the result of a secretion from the body of the ani- 

 mal ; the second, the formation of the shining ena- 

 mel. The cowries are thin and transparent, in the 

 first stages of their growth, but at length acquire 

 solidity, by means of the external layers, which the 

 animal applies after the mouth is not only formed, 

 but considerably contracted, and furnished with 

 the rudiments of teeth. The last coats proceed, 

 as we have already observed, from a transudation 

 from the wings of the animal, and leave upon the 

 convex surface of the shell the marks of the manner 

 in which they are formed. This is by a longitudinal 

 line, which divides them into two unequal parts. This 

 line, made by the junction of the wings of the ani- 



