Here is a fossil that is identified as a Notopocorystes fossil crab. It comes from the Eagle Ford Group which is part of the Cenomarian stage (about 94 mya) of the Lower Cretaceous and was found near Dallas, TX. As is typical of most fossil crabs found in the field, only the carapace is well preserved. However, you can see a small cross section of a leg in the lower right portion of the piece in the third picture. Looking at the piece it seems to have been a nodule at one point as the bottom is well rounded.
I found the age info for the formation from Lance Hall's website North Texas Fossils. He has pictures of fossils he has found in the formation and some good information about the geology of the Eagle Ford group and the region in general.