Snail Shell Mystery Solved

If you recall in my previous post about snail shells, I found a couple of empty shells that appeared to be Triodopsis but didn't have the requisite outer lip and 3 "teeth." Well, I found a shell the other day that lays this mystery to rest. These ARE Triodopsis shells, only in getting to the snail inside the predator has broken off the identifying part of the shell, including the lip with the 3 "teeth." Ideally the teeth are supposed to protect the snail, but if the predator (I'm thinking chipmunk, squirrel, even bird) has strong enough jaws or knows another effective method of breaking the shell, it can render that defense completely ineffectual and suck the snail right out of the shell. In fact, by breaking off a significant part of the outermost whorl, the predator can probably reach the snail more easily.