Quick guides - "earthworm-like" polychaetes

The following table includes some families which are quite unrelated to one another, but are nevertheless sometimes confused by inexperienced sorters, because of some superficial similarities and a generalised "earthworm-like" appearance. The interactive key to polychaete families distinguishes these exhaustively, but the following table may also help:

Arenicolidae	Arenicolidae have bodies that are greatly swollen at the anterior end (rather than being of even thickness) and heavily rugose. Non-retractile branchiae occur conspicously on many segments. The pharynx has no jaws or other hard parts. Chaetae include hooded hooks, but only in one bundle per segment (not in dorsal and ventral bundles), and hirsute-serrate capillaries.
Capitellidae	Capitellidae are small to large, with bodies that are of even thickness - "worm-like" and smooth or lightly rugose. Retractile branchiae may be present but are usually inconspicous. The pharynx has no jaws or other hard parts. Chaetae include hooded hooks, which on posterior segments occur in dorsal and ventral bundles, and smooth capillaries.
Lumbrineridae	Lumbrineridae are small to large, with bodies that are of even thickness - "worm-like"; segments are quite smooth. Eyes are absent. The pharynx carries several jaw elements - mandibles and maxillae - which are often visible without dissection as dark internal structures; the maxillae are supported by a pair of "carriers" which are much shorter than the combined mandibles. Chaetae include hooded hooks, but only in one bundle per segment (not in dorsal and ventral bundles), and smooth capillaries.
Oenonidae	Oenonidae are small to large, with bodies that are of even thickness - "worm-like"; segments are quite smooth. Eyes are present. The pharynx carries several jaw elements - mandibles and maxillae - which are often visible without dissection as dark internal structures; the maxillae are supported by a pair of long "carriers" which are much longer than the combined mandibles.
Questidae	Questids are small worms (up to about 0.1 mm wide) with bodies that are of even thickness - "worm-like". The pharynx has no jaws or other hard parts. Chaetae include hooded hooks, which on posterior segments occur in dorsal and ventral bundles, and serrated-spinose capillaries.