1. The following structural features clearly indicate that ammonoid shells were adapted to withstand considerably higher hydrostatic pressures thanNautilus shells: (1) the corrugated and marginally fluted septa gave the shell wall efficient support against implosion; (2) the secondary connecting rings could grow a great deal in thickness; and (3) the last formed chambers remained full of liquid which supported the last septum.

1. die gefalteten Septen verstärkten die Gehäusewand wirkungsvoll gegen den Wasserdruck; 2. die sekundären Siphonalhüllen hatten ein stärkeres Dickenwachstum; und 3. die zuletzt gebildeten Kammern blieben flüssigkeitsgefullt und schützten daher das letzte Septum.