Fig. 3From: Homology problems in cephalopod morphology: deceptive (dis)similarities between different types of ‘caecum’The caecum of Spirula spirula, Spirulidae, recent, Mozambique. a Lateral overview of the opened protoconch showing the caecum and prosiphon; scale bar = 100 µm. b SEM image of the opened protoconch in apical view showing the caecum and prosiphon; scale bar = 100 µm. c SEM image showing a cross fracture of the protoconch/teleoconch transition (dorsal part); scale bar 10 µm. d Camera lucida of protoconch/teleoconch transition reflecting the interactions between lamello-fibrillar caecum, inner protoconch layer, and outer sheath. e SEM image showing fractured caecum; scale bar = 100 µm. f Details of e showing the lamello-fibrillar ultrastructure of the caecum wall; scale bar = 10 µmBack to article page