Abstract 1. 1. Comparable series of chitins were derived from blue, red, stone, and horseshoe crabs by representative mild acid and EDTA decalcification followed by alkali deproteinization. 2. 2. These chitins were found to comprise a family of closely-related products with variable solubility, molecular weight, optical rotation, and acetyl values, which are a function of both the species from which they originated and their method of preparation. 3. 3. Substantial differences in the chitins were observed even from a single species, depending upon the details of their isolation.