prostomium

American  

[proh-stoh-mee-uhm] / proʊˈstoʊ mi əm /

noun

plural

prostomia

1. the unsegmented, preoral portion of the head of certain lower invertebrates.

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prostomium British  

/ prəʊˈstəʊmɪəm /

noun

1. the lobe at the head end of earthworms and other annelids: bears tentacles, palps, etc, or forms part of a sucker or proboscis

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Other Word Forms

• prostomial adjective

Etymology

Origin of prostomium

1865–70; < New Latin < Greek prostómion mouth. See pro- ², stoma, -ium

Example Sentences

Nerve cord lies in coelom; brain in first segment or prostomium in many forms.

From Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 7 "Cerargyrite" to "Charing Cross" by Various

The prostomium and the segments generally often bear processes sensory and branchial.

From Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 7 "Cerargyrite" to "Charing Cross" by Various

In both, the nephridia are all alike; there are no jaws; the prostomium rarely has processes.

From Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 7 "Cerargyrite" to "Charing Cross" by Various

The prostomium bears often processes, both dorsal and ventral, which in the Sabellids are split into the circle of branchial plumes, which surround or nearly surround the mouth in those tube-dwelling Annelids.

From Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 7 "Cerargyrite" to "Charing Cross" by Various

Further, in all members of the sub-phylum Chaetopoda the relative position of the prostomium, mouth and peristomium or first ring of the body, retains its primitive character.

From Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 6 "Armour Plates" to "Arundel, Earls of" by Various