This is a feature of members of Eunicida, the ventral and lateral walls of the buccal region are very muscular. In taxa such as Eunicidae, Onuphidae and Histriobdellidae the lining of the stomodaeum is sclerotinized into a varying number of jaw pieces. The jaws are separated into a pair of ventral mandibles and two or more pairs of lateral maxillae. In Amphinomidae and Euphrosinidae the ventral wall of the stomodaeum is also muscularized and eversible and the cuticular lining is sclerotinized. The sclerotinization is limited, so instead of forming distinct jaws, the whole ventral lining forms reinforced ridges and papillae in a file-like structure.

Aciculata: Eunicidae: Amphinomidae

Amphinomids (e.g. Eurythoe,Chloeia) have a ventral proboscis which consists of a muscular cushion armed with rasping cuticular folds which is protrusible. They are peculiar in having a ventral mouth as in the live specimen of Chloeia (it is also ventral in some eunicids but is not, as in amphinomids, circumscribed by several segments). They usually have a dorsal cushion like protuberance, at the posterior end of the prostomium, termed a caruncle. Amphinomids are often "browsers", commonly feeding by rasping sponges off rocks, the most specialized ones more or less parasitic on sponges but Chloeia is an active scavenger. In amphinomids, as seen in longitudinal section in Eurythoe, a large elongated proboscis leads to the much folded intestine.

The dorsal wall of the pharynx is relatively thin but contains well-developed longitudinal muscle fibres.The ventral side of the stomodaeum raised into elaborate inverted U-shaped cushion made up of vertical lamellae. In front of it are vascularized lips. The internal lamellar cushion is muscular and the vertical or more or less transverse edges of the lamellae have a thickened cuticle, the whole organ forming a rasping apparatus (compare the radula of molluscs). The pharynx (proboscis) is protrusible. Protractors are attached to a split buccal ring and extend from the ventral side to the body wall. Retractors extend backwards from the hinder end of this rasping organ.