Fig. 18

Harriotta raleighana (Rhinochimeridae; Holocephali; Chondrichthyes). Summary diagrams representing distribution of all tissue types in a series from rostral to caudal. Lower dental plate as three regions of developing and mature tissues that are colour coded as in the key. a rostralmost hard tissue section (Fig. 1a), outer lingual hypermineralized outer layer shown, maybe enameloid, or part of tritor (Fig. 5), b mid region from virtual section, worn surface both ovoids and tritor depicted in green (Fig. 2d), c caudal most hard tissue section in which a disjunct line shows separation of functional oral tritor from developing aboral tritor and series of new labial ovoids (Fig. 7)