Lissencephala
Lissencephala (lis`sen*sef"ȧ*lȧ) , noun, plural
[New Latin, from Greek lisso`s smooth + 'egke`falos the brain.]
(Zoology) A general name for all those placental mammals that have a brain with few or no cerebral convolutions, as Rodentia, Insectivora, etc.