Fossils in Death Valley

[Gozerian138]

Forgive me for posting about an area outside of the San Gabes/San Berboos. A buddy and I were up in Marble Canyon, in Death Valley a couple weeks ago. I saw tons of these on a hillside in the canyon. Does anybody know what kind of fossil this is? They were so abundant on the hill. They were embedded in what appeared to be ancient mud/seabed?