This snail either impaled itself on this cactus or got stuck and died. Either way, snails are ridiculous for trying to eat on some cacti.
I'm sorry I don't have an ID on this cactus, but the nursery I bought it from should be able to tell me. I think it's some kind of Echinopsis (aka Trichocereus). I bought 3 plants at the spring show and sale of the Cactus and Succulent Society of Austin and was told it was the hardiest columnar cactus to grow here. Who knows though as I've been told lots of stuff when it comes to hardy columnar cactus. I'm going to give them the best possible chance that I can though. Fortunately, they're all very small, which means I can toss a pot over them if it drops below 20F or so.