2.75x3.25x1.75" deep and 3x3.5x1.75" deep specimens containing the complete fossilized remains of 2.25" and 2" wide Zanthopsis vulgaris crabs. Zanthopsis is an extinct genus of crab. Both examples offered here are presented in what are known as "concretions." These are hard, compact masses of sedimentary rock formed by the precipitation of mineral cement within the spaces between the sediment grains. Often spherical or ovoid in shape, they sometimes include fossils, such as these crabs. The concretions are split, revealing the crabs within. Fossil crabs are rare in the fossil record, but turn up from time to time as they erode from shorelines and sea cliffs. These fossils occur in marine rocks from 40 to 25 million years old. The examples we are offering both came from the Lincoln Formation in Wahkiakum County, WA. and date to the Oligocene (35 million years ago). Both are wonderfully preserved, w/the larger specimen having one claw extended w/chela pincers open and the other claw tucked under its body. Entire carapace of the crab's main shell has been preserved during fossilization. Smaller specimen has both claws clearly visible and is missing a significant portion of the carapace, though the crab's body structure has been preserved through fossilization. A wonderful pair of fossils. From the Robert M. Overstreet Collection and comes with COA.