B.V.] THE HISTORY OF ANIMALS. 117 



use basket-nets, in order that if the purpura should fall off, 

 it may not be lost. They are most likely to fall off when 

 full, but when empty it is difficult to draw them from 

 the bait. These are the peculiarities of the purpura. The 

 nature of the ceryx is the same as that of the purpura, and 

 so are their seasons. 



7. They both have opercula, and so have all turbinated 

 shell-fish, from the period of their birth. They feed by forc- 

 ing out their tongue, as it is called, beneath the operculum : 

 the purpura has a tongue larger than a finger, with which it 

 feeds upon and pierces the conchy lia, and even the shells of 

 its own species. Both the purpura and the ceryx are long^ 

 lived, for the purpura lives six years, and its annual increase 

 is seen in the divisions on the helix of its shell. 



8. The mya also deposits nidamental capsules ; those 

 which are called limnostrea are the first to originate in 

 muddy places, but the conchae, chemae, solens, and pectens 

 find their subsistence in sandy shores ; the pinnae grow up 

 from their byssus both in sandy and muddy shores. The 

 pinnae always contain a pinnophylax, either like a small caris 

 or cancer, and soon die when this is extracted. On the whole, 

 all the testaceaare produced spontaneously in mud, different 

 kinds originating in different sorts of mud ; the ostrea is 

 found in mud, the conchae and others that have been men- 

 tioned in sand. The tethya, balanus, and others which live 

 on the surface, as the patella and nerita, originate in holes 

 in the rocks. All these reach maturity very soon, espe- 

 cially the purpurse and pectens, for they are matured in one 

 year. 



9. Very small white cancri are produced in some of the 

 testacea, especially in the myae that inhabit muddy places, 

 and next to this in the pinnae those which are called pinno- 

 terae ; they occur also in the pectens and limnostrea. These 

 animals apparently never grow ; and the fishermen say that 

 they are produced at the same time as the creatures they 

 inhabit. The pectens disappear for some time in the sand, 

 and so do the purpurse. The ostrea (bivalves) are produced 

 in the manner described, for some of them originate in 

 shallow water, others near the shore, or among rocks, or in 

 rough hard places, or in sand ; and some have the power 

 of locomotion, others have not. 



