Fig. 1. Pteromys Sabrinus, Pennant. Severn-River Flying Squirrel. Fig. 2. Pteromys Alpinus, rich. Rocky Mountain Flying Squirrel.

Following the great success of his “The Birds of America” lithograph portfolio project John James Audubon began his next project "The Viviparous Quadrupeds of North America". Viviparous Quadrupeds oft...