U, IV.] THE HISTORY OF ANIMALS. 83 



right-handed, and move, not in the direction of the helix, 

 but the contrary way. 



6. The external parts of these creatures are thus distin- 

 guished ; the nature of their internal structure is similar 

 in all, especially in the turbinated animals, for they differ 

 in size and in the relations of excess, the univalves and 

 bivalves do not exhibit many differences. Most of them 

 have but few distinctive marks from each other, but they 

 differ more from the immovable creatures. This will be 

 more evident from the following considerations. In na- 

 ture they are all alike, the difference, as before said ; is in 

 excess ; for in larger species the parts are more conspicuous, 

 and less so in those that are smaller. They differ also in 

 hardness and softness, and such like affections. 



7. For all have on the outside of the shell, in the mouth, 

 a hard piece of flesh, some more, some less ; from the middle 

 of this are the head and the two horns ; these are large in 

 larger species, in the little ones they are very small. The 

 head is protruded in the same manner in all of them, and 

 when the creature is alarmed it is again retractef; some 

 have a mouth and teeth, as the snail, which has small, sharp, 

 and smooth teeth. 



8. They have also a proboscis, like that of the fly, and this 

 organ is like a tongue. In the ceryx and the purpura this 

 organ is hard, like that of the my ops and oestrus, with which 

 they pierce through the skins of quadrupeds ; but this is 

 more powerful in strength, for they can pierce through the 

 shells of the baits. The stomach is joined quite closely to 

 the mouth ; the stomach of the cochlus is like the crop of a 

 bird ; below this there are two hard white substances like 

 nipples, which also exist in the sepia, but are much harder. 



9. From the stomach a long, simple intestine reaches as far 

 as the spiral, which is on the extremity of the body. These 

 are distinct, and in the purpura and the ceryx are in the 

 helix of the shell. The bowel is continuous with the intes- 

 tine. The intestine and bowels are joined together, and are 

 quite simple, to the anus. The origin of the bowel is around 

 the helix of the mecon, 1 and here it is wider. The mecon is, 

 as it were, a superfluous part in all testacea, afterwards an- 

 other bend causes it to return to the fleshy part ; the end of 



1 The so-called liver (Strack). Papaver (Scaliger). 



G 2 



