Opinions from J. Leidy 1858
- 'Aelurodon ferox belongs to Aelurodon'
- 'Anchitherium (Hypohippus) belongs to Anchitherium'
- 'Anchitherium (Parahippus) belongs to Anchitherium'
- 'Anchitherium (Parahippus) cognatus belongs to Anchitherium (Parahippus)'
- 'Canis (Epicyon) belongs to Canis'
- 'Canis (Epicyon) haydeni belongs to Canis (Epicyon)'
- 'Canis dirus belongs to Canis'
- 'Canis saevus belongs to Canis'
- 'Canis temerarius belongs to Canis'
- 'Canis vafer belongs to Canis'
- 'Castor (Eucastor) belongs to Castor'
- 'Castor (Eucastor) tortus belongs to Castor (Eucastor)'
- 'Cervus warreni belongs to Cervus'
- 'Elephas (Euelephas) belongs to Elephas'
- 'Elephas (Euelephas) imperator belongs to Elephas (Euelephas)'
- 'Equus (Protohippus) belongs to Equus'
- 'Equus (Protohippus) perditus belongs to Equus (Protohippus)'
- 'Equus excelsus belongs to Equus'
- 'Felis (Pseudaelurus) intrepidus belongs to Felis (Pseudaelurus)'
- 'Hystrix (Hystricops) belongs to Hystrix'
- 'Hystrix (Hystricops) venustus belongs to Hystrix (Hystricops)'
- 'Mastodon (Tetralophodon) belongs to Mastodon'
- 'Mastodon (Tetralophodon) mirificus belongs to Mastodon (Tetralophodon)'
- 'Megalomeryx niobrarensis belongs to Megalomeryx'
- 'Merychippus mirabilis belongs to Merychippus'
- 'Merychyus elegans belongs to Merychyus'
- 'Merychyus major belongs to Merychyus'
- 'Merychyus medius belongs to Merychyus'
- 'Merycochoerus proprius belongs to Merycochoerus'
- 'Procamelus occidentalis belongs to Procamelus'
- 'Pseudaelurus was reranked as Felis (Pseudaelurus) and belongs to Felis'
- 'Rhinoceros crassus belongs to Rhinoceros'
- 'Stylemys was reranked as Testudo (Stylemys) and belongs to Testudo'
- 'Testudo (Stylemys) niobrarensis belongs to Testudo (Stylemys)'