A, Siphonal notch of the shell e, Everted buccal introvert (prooccupied by the siphonal boscis).
H', Prolonged siphonal notch of the shell occupied by the siphon, or trough-like process of the mantle-skirt.
Ac, Siphonal notch of the mouth of the shell.
(I) Animal removed from its shell, a probe g passed into the sub-pallial chamber through the excurrent siphonal notch.
D, Excurrent siphonal notch of the mantle margin.
Incurrent siphonal notch of the mantle margin.
Probe passed into the superior division of the subpallial chamber through the excurrent siphonal notch, and issuing by the side of the foot into the inferior division of the sub-pallial chamber.
1, d); the lower space communicates by the lower siphonal FIG.
It is through this passage, or indirectly through the pores of the gill-plates, that the water introduced into the lower subpallial space must pass on its way to the excurrent siphonal notch.
The food of the Anodonta, as of other Lamellibranchs, consists of microscopic animal and vegetable organisms, brought to the mouth by the stream which sets into the sub-pallial chamber at the lower siphonal notch (e in fig.
Megalodontidae.-Shell 1a, tr, Upper and lower inequilateral, thick; posterior siphons adductor impression on a myo ms, Siphonal muscle of the phorous apophysis.
Mytilus possesses no siphonal tube-like productions of the margin of the mantle-skirt, nor any notching of the same, representative of the siphons which are found in its fresh-water ally, the Dreissensia polymorpha.