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Hi Everyone. I found this gastropod at Whiskey Bridge, near Bryan, Texas two years ago which so far I've been unable to identify. Whiskey Bridge is a marine Eocene site, Crockett Formation, Stone City Member. The specimen is between a half and three quarters of an inch. Thanks. Any ideas would be appreciated.

As background, I am a sedimentologist, and my father was a vertebrate paleontologist, and I am reasonably good at broad-brush identification of fossils (especially in carbonates), but when it comes to any kind of detailed ID, it's not really my area! My son (9) is really into fossils (not my fault, I swear!), and I took him to the nearest place that I knew we would be able to collect some fossils for him, which was Whiskey Bridge near College Station, TX. Here, on the banks of the Brazos River, the Eocene Crockett Fm. is exposed, and we were collecting in the Stone City Member. We found plenty of gastropods, pelecypods, and scaphopods, but a disappointing (for him) lack of shark teeth. The outcrop is mostly glauconitic mudstones, which contained most of the fossils, but there were also lenses of fine sandstone between some of the glauconitic layers. These have been described as tidalites, but the sedimentologist in me would happily argue that they could also be hummocky cross-stratified storm beds. The exposures are pretty poor, so this wouldn't be a very satisfying argument to have. While scraping through the extremely friable (tidal? event bed?) sandstones, I came across the fossil seen in the pictures here. My first reaction was some kind of tooth, but I haven't seen one with this shape before, and I have my doubts about that. It is somewhat triangular in cross section, with a curved 'front' and a nearly flat 'back', and the 'back' is shiny (almost opalescent), something that doesn't come through well in the photos. The length is ca. 20 mm, and it is approximately 5 mm across. All of the shelly material out of here was bleached white, so I don't think it's a weird section of a shell. There were concretions in the sandstone, but they were lenticular in shape and genarlly 10 cm+ across (nor have I ever seen a concretion with a backwards curved shape like this). There were hints of burrowing in the sandstone, but again, the shape doesn't even somewhat resemble any burrows I've seen (I can do a better job of identifying trace fossils than I can real fossils), so I don't think it's a mineralized trace fossil. Any ideas would be greatly appreciated!