1 Spicular sheath covered with small spines................................................................. 2
- Spicular sheath non-spiny............................................................................. 3
2 Male tail lacks membranous bursa; either two large caudal ventro-lateral lobes each with a papilla at the base, or lobes absent with only one pair of papillae; eggs with short polar plugs either not or only slightly protruding from egg shell.... Capillaria
- Male tail with membranous bursa supported by two lateral finger-shaped processes (rays) and one pair of papillae at their base; unpaired dorsal caudal projection present; polar plugs slightly protruding from egg shell................. Piscicapillaria
3 Male tail with membranous bursa supported by two narrow digital projections (rays) adhering to rounded body end................................................................................................ Paracapillaria
- Male tail without membranous bursa but with two large, spherical ventro-lateral lobes bearing a pair of small indistinct papil- lae.................................................................................... Pseudocapillaria