23 Nissan (Shemini)

Why does it say by all of the treif animals with one siman (either it chews its cud or it has split hooves) in Vayikra 11,4-7, that you can't eat it because... and then list the siman it does have then the siman it doesn't have? Why doesn't it just say that you can't eat it because it doesn't have the siman it doesn't have? There's no reason to say the siman it does have!