Sandia Cave is located in an escarpment of Pennsylvania limestone in Ellis Canyon, thirty miles northeast of Albuquerque, New Mexico. It presents an interesting problem in regard to the time when man existed in North America contemporaneously with the horse (equus?), the ground sloth (nothrotherium), and other extinct Pleistocene forms. In the United States, discoveries of artifacts with extinct mammals do not show necessarily that man existed in the Pleistocene or ice age, but may indicate that the mammals have survived that period and become extinct in more recent times. The best criteria for dating would be collections made in the glaciated areas and associated with glacial deposits. However, this is not always possible, and other means must be sought. Dating can be done to some degree of accuracy by the interpretation of climatic conditions that existed at the time the deposits were laid down.