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The group that includes all ordinary or placental mammals; the Placentalia. See Mammalia.

A subclass of Mammalia, having a cloaca in which the ducts of the urinary, genital, and alimentary systems terminate, as in birds. The female lays eggs like a bird. See Duck mole, under Duck, and Echidna.

g certain important characters in common; as, the Carnivora and Insectivora are orders of Mammalia.

The formation of ova or eggs in the ovary, and the discharge of the same. In the mammalian female the discharge occurs during menstruation.

Same as Mammalia.

A division of Mammalia including those that have a placenta, or all the orders above the marsupials.

The fifth ventricle in the mammalian brain. See Ventricle. B. G. Wilder.

eveloped in Northwestern New Mexico, along the Rio Puerco, and are characterized by their mammalian remains.

An order of extinct Mammalia found in the Tertiary formations.

An extinct group of Mammalia found fossil in the Eocene formation. The species are related to the carnivores, ungulates, and rodents. Called also Tillodonta.

An extinct order of Mammalia found in the South American Tertiary formation. The incisor teeth were long and curved and provided with a persistent pulp. They are supposed to be related both to the rodents and ungulates. Called also Toxodontia.

A theory of the development of mammalian molar teeth. The primitive stage is that of simple cones, as in reptiles. The simple cone then developed a smaller cone in front and another behind. Next, a cingulum was developed, and the three cones became arranged in a triangle, the two smaller cusps having moved to the outer…

An extensive division of Mammalia including those having claws or nails, as distinguished from the hoofed animals (Ungulata).

nd a ventral, or visceral, cavity below it. The subdivisions or classes of Vertebrata are Mammalia, Aves, Reptilia, Amphibia, Pisces, Marsipobranchia, and Leptocardia.

A division of Mammalia in which the placenta is zonelike.