The morphology of the body wall and musculature of the marine triclad Palombiella stephensoni (Palombi, 1938) is described. The epidermis possesses a system of internal "channels"; these could be part of a mechanism protecting the epidermis from damage. It is suggested that the structure termed "basement membrane" by other workers is best called a "connective" layer. One type of subepidermal gland opens to the exterior by a system of branching ducts which penetrate epidermal cells, which indicates a complex "channel" system within these epidermal cells. The musculature conforms to the usual pattern for a marine triclad.