I guess those names were the scientific names for the different squirrels. The first name is the genus name (family) and the last is the species name. Evidently the first fox squirrel seen and named was a black or dark color as the species name is niger meaning dark or black. Most of our common animals were ‘named’ by early scientists working in the Southern Atlantic states. The common gray squirrel got the species name of carolinensis as it was probably identified first in one of the Carolinas. Virginia is also a state where many plants and animals were also first identified. The scientific name for whitetailed deer is Odocoileus virginianus. Most scientific names describe the outstanding characteristic of the plant or animal or where it was first identified. If you want to see some of the color variations of the fox squirrel do an image search on Goggle. The mule deer is named Odocoileus hemionus. The hemionus refers to the mule or wild ass like ears of that deer. The mule deer and the whitetailed deer evidently are closely enough related to interbreed where their ranges overlap. It is usually the more aggressive whitetail bucks that breed with the mule deer does. The off spring share characteristics of both species especially where the antlers are concerned. Whether these offspring are fertile or not I can’t remember. If not, it might help to explain the decline in the numbers of mule deer in certain areas that I have been hearing and reading about. As I am living in Missouri I have no personal experience with Mule deer, just what I have read.
RJ