butterfly crab

Hart, Josephine F. L. (1965-05-04), “Life History and Larval Development of Cryptolithodes typicus Brandt (Decapoda, Anomura) from British Columbia”, in Crustaceana, volume 8, issue 3, DOI:10.1163/156854065X00460, JSTOR 20102652, pages 255–276: “The turtle or butterfly crab, Cryptolithodes typicus Brandt, 1849, is a crustacean of … the family Lithodidae.”