Enteric pouch of the umbrella, in the left-hand figure, points to the cavity uniting neighbouring pouches near the margin of the umbrella and giving origin to TCa, the tentacular canal.
Tentacular blood-vessel arising from the cut arm-vessel in the small arm-sinus.
Thus in the recently discovered arctic genus Prosorhynchus the muscular and glandular extremity is protrusible, but in the allied Gasterostomum this organ is represented by a sucker with fimbriated or tentacular margins.
The vestibule of the mouth is the space bounded by the oral hood; this arises by secondary downgrowth of lid-like folds over the true oral aperture, and is provided with a fringe of tentacular cirri, each of which is supported by a solid skeletal axis.
At the base of the head dorsally are a pair of flat tentacular lobes from the edges of which the cephalic filaments or captacula arise.
