Ridge Group: HISTIOTEUTIDAE / ONYCHOTEUTHIDAE.

　　Medium size beak; LRL > 2HL; wing fold high with a deep and wide groove
---Histioteuthis corona inermis
　　　

　Medium size beak; LRL = 1.5 HL; wing fold low with a shallow and wide groove
---Histioteuthis celataria pacifica
　　　

　Large size beak; LRL = 1.5 HL; wing fold raised up like ridge with deep groove---Histioteuthis dofleini
　　　

　Medium size beak; LRL = 1.5 HL; wing fold low; jaw angle visible;
ridge on lateral wall prominent in small beak and broaden in larger beak
---Onychoteuthis borealijaponica　　Onychoteuthis banksii
small beak　　large beak
*Same size lower beaks of O. borealijapnica and O. banksii resemble each other. Lower beak of O. banksii tends to have relatively larger rostrum
with weaker ridge on lateral wall but close comparison with reference collection is needed for identification.