157. Jamieson, B.G.M., Guinot, D., Tudge, C.C. and Richer de Forges, B. 1997d. Ultrastructure of the spermatozoa of Corystes cassivelaunus (Corystidae), Platepistoma nanum (Cancridae) and Cancer pagurus (Cancridae) supports recognition of the Corystoidea (Crustacea, Brachyura, Heterotremata). Helgolander Meeresuntersuchungen 51, 83-93.
A combination of characters, not individually unique, possessed by the
  corystid, Corystes cassivelaunus, and the two cancrids, Platepistoma nanum
  and Cancer pagurus, defines a corystoid-type of spermatozoon: the basally
  bulbous, anteriorly narrowing perforatorium, the extent of this almost to
  the plasma membrane through a widely perforate operculum, and the simple
  inner acrosome zone, lacking an acrosome ray zone. The sperm of the two
  cancrids are closely similar, that of the corystid differing, for
  instance, in the less pointed, and less tapered, form of the
  perforatorium. This relative uniformity of spermatozoal ultrastructure in
  the cancrid+corystid assemblage so far investigated supports inclusion of
  the two families in the superfamily Corystoidea by Guinot (1978). The
  combination of perforation of the operculum and absence of an acrosome ray
  zone (at least in a clearly recognizable form) are features of the
  Potamidae which possibly indicate that the latter family, modified for a
  freshwater existence, is related to the cancrid+corystid assemblage. Some
  elongation of the centrioles, apparent at least in Corystes, may be a
  further link with potamids in which they are greatly elongated. The
  coenospermial spermatophores of cancridoids are a notable difference from
  the cleistospermia of potamids; but the latter is probably an apomorphic
  modification for fertilization biology.