from The Century Dictionary.
- Placental mammals; those mammals which are placentate or placentiferous: distinguished from
from the GNU version of the Collaborative International Dictionary of English.
- noun plural (Zoöl.) A division of Mammalia including those that have a placenta, or all the orders above the marsupials.
Sorry, no etymologies found.
As the large and blood-filled vascular network of the foetal allantois attaches itself closely to the mucous lining of the maternal womb, and the partition between the blood-vessels of mother and child becomes much thinner, we get that remarkable nutritive apparatus of the foetal body which is characteristic of the placentalia (or choriata).