Opinions from E. D. Cope 1890
- 'Agabelus belongs to Platanistidae'
- 'Anarnak is corrected as Anarnacus and belongs to Physeteridae'
- 'Archaeoceti belongs to Cetacea'
- 'Balaena belongs to Balaenidae'
- 'Balaena prisca is recombined as Cetotherium priscum'
- 'Balaenoptera belongs to Balaenidae'
- 'Balaenoptera pusilla is recombined as Cetotherium pusillum'
- 'Balanadae is corrected as Balaenidae and belongs to Mysticeti'
- 'Belemnoziphius prorops is recombined as Mesoplodon prorops'
- 'Berardius belongs to Physeteridae'
- 'Cetophis belongs to Platanistidae'
- 'Cetophis heteroclitus belongs to Cetophis'
- 'Cetotherium belongs to Balaenidae'
- 'Choneziphius belongs to Physeteridae'
- 'Choneziphius trachops belongs to Choneziphius'
- 'Colophonodon holmesii is recombined as Squalodon holmesii'
- 'Delphinapterus belongs to Delphinidae'
- 'Delphinapterus orcinus belongs to Delphinapterus'
- 'Delphinidae belongs to Odontoceti'
- 'Delphinus belongs to Delphinidae'
- 'Delphinus (Grampus) was reranked as Grampus and belongs to Delphinidae'
- 'Delphinus calvertensis is recombined as Lophocetus calvertensis'
- 'Delphinus canaliculatus is recombined as Stenodelphis canaliculatus'
- 'Delphinus vermontana is recombined as Delphinapterus vermontanus'
- 'Dinoziphius carolinensis is recombined as Hoplocetus carolinensis'
- 'Eschrichtius cephalus is recombined as Cetotherium cephalus'
- 'Eschrichtius davidsonii is recombined as Balaenoptera davidsonii'
- 'Eschrichtius leptocentrus is recombined as Cetotherium leptocentrum'
- 'Globicephala belongs to Delphinidae'
- 'Graphiodon vinearis is recombined as Squalodon vinearius'
- 'Herpetocetus belongs to Balaenidae'
- 'Hoplocetus belongs to Physeteridae'
- 'Hyperoodon is a subjective synonym of Anarnacus'
- 'Ixacanthus belongs to Platanistidae'
- 'Ixacanthus coelospondylus belongs to Ixacanthus'
- 'Kogia belongs to Physeteridae'
- 'Lagenorhynchus belongs to Delphinidae'
- 'Macrophoca atlantica is recombined as Squalodon atlanticus'
- 'Megaptera belongs to Balaenidae'
- 'Megaptera expansa is recombined as Cetotherium expansus'
- 'Mesoplodon belongs to Physeteridae'
- 'Mesoteras belongs to Balaenidae'
- 'Mesoteras kerrianus belongs to Mesoteras'
- 'Monodon belongs to Delphinidae'
- 'Mysticeti belongs to Cetacea'
- 'Neomeris belongs to Delphinidae'
- 'Odontoceti belongs to Cetacea'
- 'Orca belongs to Delphinidae'
- 'Palaeocetus belongs to Balaenidae'
- 'Phocaena belongs to Delphinidae'
- 'Physeter belongs to Physeteridae'
- 'Physeter macrocephalus belongs to Physeter'
- 'Physeteridae belongs to Odontoceti'
- 'Physeterula dubusii is recombined as Kogia dubusii'
- 'Physodon belongs to Physeteridae'
- 'Platanista belongs to Platanistidae'
- 'Platanistina was reranked as the family Platanistidae and belongs to Odontoceti'
- 'Plesiocetus belongs to Balaenidae'
- 'Pontoporia belongs to Platanistidae'
- 'Priscodelphinus belongs to Platanistidae'
- 'Priscodelphinus grandaevus belongs to Priscodelphinus'
- 'Rhabdosteus belongs to Platanistidae'
- 'Rhabdosteus latiradix belongs to Rhabdosteus'
- 'Rhachianectes [misspelled as Rachianectes] belongs to Balaenidae'
- 'Sagmatias belongs to Delphinidae'
- 'Squalodon belongs to Squalodontidae'
- 'Squalodon antverpiensis belongs to Squalodon'
- 'Squalodon grateloupii belongs to Squalodon'
- 'Squalodontidae belongs to Odontoceti'
- 'Stenodelphis belongs to Platanistidae'
- 'Stenodon is a subjective synonym of Orycterocetus'
- 'Trirhizodon belongs to Squalodontidae'
- 'Zarhachis belongs to Platanistidae'
- 'Zeuglodon belongs to Zeuglodontidae'
- 'Zeuglodon brachyspondylus belongs to Zeuglodon'
- 'Zeuglodon cetoides belongs to Zeuglodon'
- 'Zeuglodontidae belongs to Archaeoceti'