Measurement of density and thickness of cuticle of an array of decapod crustaceans indicates that cuticle tends to be thick and dense in benthic organisms and thinner and less dense in nektobenthic decapods. Thin section analysis of the cuticle under crossed polarized light documents a broad range of area of biomineralization. Cuticle density is strongly correlated with area of calcification. One of the nektobenthic decapods in the study exhibited no calcification of the cuticle at all, and thus exhibited the lowest density. These data support the hypothesis that density and thickness of cuticle contribute to adaptation to benthic and nektobenthic lifestyles.