Order HEXANCHIFORMES
Introduction
The order Hexanchiformes comprises two families of deepwater sharks, characterised by six or seven gill slits, in contrast to the five in other sharks (Compagno 1984).
General References
Compagno, L.J.V. 1984. FAO Species Catalogue. Sharks of the World. An annotated and illustrated catalogue of shark species known to date. Hexanchiformes to Lamniformes. FAO Fisheries Synopsis No. 125. Rome : FAO Vol. 4(1) pp. 1-249
Shirai, S. 1992. Identity of extra branchial arches of Hexanchiformes (Pisces, Elasmobranchii). Bulletin of the Faculty of Fisheries, Hokkaido University 43(1): 24-32