The Importance of the Facial Pit of the Northern Pacific Rattlesnake
The Importance of the Facial Pit of the Northern Pacific Rattlesnake(Crotalus viridis oreganus) Under Natural Conditions in Southern British Columbia.
An MSc thesis submitted by William Barton Preston UBC, 1964.
See full PDF : preston_1964_importance_of_facial_pit_of_north_pac_rattlesnake_southern_bc_thesis
reference: The Western ratttlesnake: