Superficial features / Michael J. Tyler and Margaret Davies -- Natural history / Glen Ingram -- Oral birth and perinatal behaviour / Michael J. Tyler -- Larval development / Michael J. Tyler and Margaret Davies -- Skeleton / Margaret Davies -- Musculature / Thomas C. Burton -- Reproductive system / Philippa Horton -- Structural changes to stomach and oesophagus / Joseph C. Fanning -- Inhibition of gastric secretion / Paul O'Brien and David Shearman -- Evolution of gastric brooding / Michael J. Tyler -- Phylogenetic relationships / Michael J. Tyler -- Miscellany / Michael J. Tyler