Lateralis

The white-tailed pronghorn squirrel (Ammospermophilus leucurus) lives in the hot desert shrub lands of the western valleys, while the golden-mantled ground squirrel (Spermophilus lateralis) lives throughout the mountains.

Sometimes, a third region, the pars lateralis, is mentioned, though it is usually classified as part of the pars reticulata.

This is a reminder of the common origin of these two vibration- and sound-detecting organs that are grouped together as the acoustico-lateralis system.