Dipolydora tetrabranchia (Hartman 1945)

Polydora tetrabranchia Hartman

Hartman, 1945, p. 34, pl. 1: figs. 7–10.

MATERIAL EXAMINED.—North Carolina (Beaufort, Types, AHF N1563).

DESCRIPTION.—This is a small species, measuring about 6 mm in length and having about 30 segments. The prostomium has a weak anterior incision. There are no eyes or nuchal tentacle. The caruncle extends to setiger 1.

In the specimens examined, notosetae were not seen on setiger 1, although Hartman (1945) indicated they were present. Slender, fine, winged, capillary notosetae occur in setigers 2–4, 6, and succeeding segments. The neuropodia of setigers 1–4 and 6 contain winged capillary setae. Hooded hooks begin on setiger 7 with no more than three hooks per segment. They have the main fang bent at nearly a right angle to the recurved shaft (Figure 7a).

The modified spines of setiger 5 are distally bifid, with two large teeth (Figure 7b–c). There are usually two or three spines in each parapodium, accompanied by slender pennoned setae.

The pygidium is a simple, collar-like ring.

Branchiae begin on setiger 7 and usually number only four pair.

DISTRIBUTION AND ECOLOGY.—Polydora tetrabranchia bores in shell fragments and is known only from Beaufort, North Carolina.