Cycloteuthidae can be split into two genera: Cycloteuthis and Discoteuthis. They can be distinguished by fin shape. Cycloteuthis has fins which angle towards a long tail, while Discoteuthis has oval shaped fins (hence the name)
Discoteuthis
Cycloteuthis
Info at:
Cycloteuthidae
Discoteuthis
Cycloteuthis
Info at:
Cycloteuthidae