diacresis

Transverse groove on posterior of exopod (rarely also endopod) of uropod appendage, in some forms dividing exopod into 2 movably connected parts [Moore and McCormick, 1969].

Transverse groove on posterior part of exopod (also rarely of endopod) of uropod; sometimes dividing exopod into 2 movable parts [McLaughlin, 1980].