Limulus

Abstract

CONCERNING the systematic place of Limulus, I should like to draw attention to a habit which has, as far as I know, never been alluded to in discussions, viz. the manner of casting its skin, mentioned by me in Deformation of Insects (Mem. Compar. Zoology). Limulus splits the skin exactly around the front margin of the head. Among Crustacea the Decapods at least split the skiri around the hind margin of the carapace. Insects split the skin in the longitudinal middle line of the occiput and thorax, with the later addition of a transversal split on the head. I have seen cast skins of Scorpio, Pseudoscorpions, Hydrachna, and Arachnids, but they are not now at hand for a sure verification. As far as I remember all of them split the skin in the middle line of the anterior parts. At least I do not remember to have seen any transversal anterior split.