Deтodex zalophi Sp. nov. from the california sea lion (Zalophus californianus) is described. It is а moderate-sized elongate member of the genus which resides in the hair follicle. Epithelial destruction and undercutting nеаг the mouthparts indicate cytophagy: thickened keratin nеаг podosoma and opisthosoma suggests induced hyperkeratinization possibly Ьу strong leg claws. Тhе discovery of оnе female and four males of D. zalophi invested Ьу а single sheath of keratin and а 1: 3.2 sex ratio indicates arrhenotoky. D. zalophi was recovered from the skin of sea lions (Pinnipedia) in captivity in California, Texas and Australia. It is the first demodicid to bе described from а rnarine mammal.