This is an Atlantic horseshoe crab (Limulus polyphemus) on drafting film. Both sides of the film contain pigment. The front side is done in carbon dust and the crab's darkest darks are achieved with ink on the back side of the film. 
The piece measures 11 x 14 inches and is shown in the photos with a gray mat and a simple pop-in frame. The price listed is for the art only, but if you wish to purchase the mat and frame also, need framing advice or help, please contact me.