152 History of Nature. [BooK IX. 



their Shells, and, for want of Nourishment, diminish in size. 

 But if it Thunder, suddenly they shut their Shells through 

 Fear, and produce those which are called Physeinata, a 

 Kind resembling an empty Bladder blowed up with Wind, 

 without any Body ; and these are the Abortions of Shells. 

 Those which are sound are formed of many Skins, which 

 may not improperly be thought the solid Substance of the 

 Body; which they that are skilful cleanse them from. I 

 wonder that they so greatly rejoice in the Air; for with the 

 Sun they become red, and lose their Whiteness, just like the 

 Body of a Man. Therefore those Shells that keep in the 

 main Sea, and lie deeper than the Sunbeams can pierce to 

 them, have the finest Pearls. And even these become yellow 

 with Age, and dull with Wrinkles; so that the Lustre which 

 is so much sought for, only continued! during their Youth. 

 When they are old, they grow thick, and stick fast to the 

 Shells, so that they cannot be separated but with a File. 

 These have only one Face, and from that Side are round ; 

 for the back Part is flat ; for which Reason such are called 

 Tympania. We may see them growing together in these 

 Shells which serve to carry Ointments. 1 There is a Pearl 

 that, is soft when in the Water, but when taken out it pre- 

 sently hardeneth. When this Shell perceiveth the Hand, 

 it shutteth itself, and so covereth over her Riches, being 

 aware that it is for these she is sought after. But if the 

 Hand come in the Way of the Shell, it will be cut off by its 

 sharp Edge ; and the Punishment cannot be more just, 

 although she is armed with other Means of Revenge. For 

 they keep for the most Part about Rocks ; and if they are 

 in deep Water they are accompanied with Sea-dogs. And 

 yet all this will not keep them away from the Ears of the 

 Ladies. Some say that, like Bees, every Company of these 

 Shells has one Chief, distinguished for his Size and Age, 



1 These boxes, made of beautifully -coloured shells, and ornamented 

 with rare pearls, for holding precious unguents, will remind the reader of 

 the alabaster box for the same purpose spoken of in the Gospels. From 

 what Pliny says of these alabaster boxes, they must have been turned 

 with a lathe. Wern. Club. 



