The southwestern desert regions are credited with harboring several genera of snakes whose grooved back teeth indicate that they may have poisonous properties. Of these, the Sonora lyre snake[11] (Trimorphodon lambda) and the Mexican vine snake (Oxybelis aeneus auratus) are the only species of sufficient size to be considered as even remotely dangerous to mankind. Species of the genera Tantilla (black-headed snake), Hypsiglena, and Sonora are too small and too difficult for the amateur to identify to be considered in this publication.