Key to species of Ascarophis

1 Tufts of filaments on both poles of eggs; left spicule 0.59–0.88 long...................................... A. arctica

- Filaments on only one egg pole........................................................................... 2

2 Left spicule <0.15 long. Females 7.1– 9.4 long................................................... A. sebastodis

- Left spicule> 0.50 long. Females 8.5–12.7 long................................................... A. morrhuae

3 Left spicule between 0.25 and 0.40 long................................................................... 4

4 Females 5.9–8.7 long........................................................................ A. extalicola

- Females 19.3–35.9 long....................................................................... A. filiformis