Fig. 5From: The internal structure of varices and constrictions in Jurassic and Cretaceous ammonoid shellsInternal structure of ridges (growth direction left). a, b Ptychophylloceras cf. dacquei JOLY (MAn-4515), a young varices are characterized by smooth surface, b older varices are accompanied by a ventral ridge, the outer relief is formed by the outer prismatic layer; c Desmoceras latidorsatum MICHELIN (MAo-1788), in ventral position only ridges are formed; the outer prismatic layer forms the relief which is compensated by the nacre layer and the inner prismatic layer. dipl dorsal inner prismatic layer, ipl inner prismatic layer, ncl nacre layer, opl outer prismatic layer, S septum, pel pelicula, wl wrinkle layerBack to article page