Fig. 3

Richtersius coronifer s.s. (Richters, 1903) from the Billefjorden population, mouth seen in SEM. a head and mouth opening of a hatchling. b oral cavity armature of an adult. Asterisk indicates the circular sensory field, filled arrows indicate the peribuccal velum/lamina, filled arrowheads indicate the first band of teeth, filled indented arrowhead indicates the pre-mouth ventricle, empty indented arrowheads indicate the teeth of the second band, dorsal and ventral teeth of the third band are marked with D and V, respectively. Scale bars in μm