Key to the species of the genus Cyllopus

1 Gnathopod 1 simple. Gnathopod 2; carpal process extends to middle of propodus. Pereopod 7 with oval basis ................................................. C. magellanicus Dana, 1853

­ Gnathopod 1 weakly chelate. Gnathopod 2; carpal process extends to limit of propodus. Pereopod 7; basis triangular with concave posterior margin.................................. ...................................................................................................... C. lucasii Bate, 1862