Fig. 3

Harriotta raleighana (Rhinochimeridae; Holocephali; Chondrichthyes). Microstructure of ovoids using different optical methods to illustrate tissue composition, during their formation. a incident reflected light (as in Fig. 1a), ovoids within sclerotic dentine (ov, sod), oral mature hypermineralized ovoid (grey), but two adjacent ones are in transition (white). b, c single mature ovoid taken in polarized light with a gypsum plate (see also Fig. 11e), delicate tubules (tu) radiate from the periphery where capsular fibres (cap) surround the whole hypermineralized dentine, also blood vessels (vas) gather here and cell body spaces for odontoblasts (cbs); in C tubules are seen to connect with these peripheral cell body spaces (asterisk), as also in B; the blue colour shows some oriented birefringent structure, early oriented crystals of hydroxyapatite, (see Fig. 9c, d, Fig. 11a, d). d–f transmitted light with Nomarsky optics of early ring of formed ovoid tissue (ov) through which tubules run, surrounding a centre of disorganized granular mineral (gr), opaque to light; e, f higher magnifications of D, of tubules in peripheral dentine (tu) and F of the centre with saccules (asterisk), tubules and granules in clustered groups (see Fig. 9g, h)