This is the Atlantic horseshoe crab, also known as the *Limulus polyphemus*. Despite their name, they are actually more related to spiders and scorpions than they are to crabs.
For more info: https://en.wikipedia.org/wiki/Atlantic_horseshoe_crab
Accession number: 5.16
Captured with Artec Spider 3D Scanner https://www.artec3d.com/portable-3d-scanners/artec-spider-v2