Observations of P. m''callii in the Coachella Valley of California show that it is primarily an arenicolous form. Numerous adaptations to sand-dwelling existence include a dorso-ventrally flattened body and tail, scalation changes facilitating rapid burial in the sand, and remarkable protective coloration. A modified form of sand swimming was observed. The opt. activity temp. range was found to be from 35[degree]C to 41[degree]C. Temp. control mechanisms are discussed. Heavy nematode infestation was noted in stomach analysis and seems to be correlated with the animals'' strict diet of ants.