Dipodomys, which has the molars rootless, is typified by D.
They may be " rootless " masses brought upon the top of the later beds by thrustplanes.
The premolars and molars may be rooted or rootless, with tuberculated or laminated crowns, and are arranged in an unbroken series.
- Vertical and Longitudinal Section through the Skull of the Beaver (Castor fiber), showing the brain-cavity, the greatly developed plates of bone in the nose-cavity, the mode of implantation of the ever-growing chisel-edged incisor, and the curved rootless cheek-teeth.
Rootless, and either cusped or formed of parallel plates, this diversityof structure often occurring in the same family.