Fig. 4 in Comparative morphology and phylogenetic significance of Gregory's diverticulum in sand dollars (Echinoidea: Clypeasteroida)

Fig. 4 Absence of Gregory's diverticulum in Marginoproctus (a–e) as well as presence and shape of the organ in the Scutellidae (f–o) and Dendrasteridae (p–t). The figure shows selected X-ray images and a photograph of a dissected specimen. a–e Marginoproctus djakonooi (3, 3, 5, 6, 9 mm test length); f–j Scaphechinus griseus (2, 6, 9.5, 35, 36 mm);