Distribution. E Venezuela (Sierra de Lema, Bolivar) and W Guyana (Mt Ayanganna, Potaro-Siparuni Region). Descriptive notes Head—body 12-1 cm, tail 7-4 cm. Measurements from the holotype, the only known adult, but weight was not reported. Specimens of Reig's Opossum from Guyana weighed 19 g, but they were subadults. Dorsal fur is uniformly dark brown, darker on rump and slightly darker or more reddish on head and neck. There are no mid-rostral stripe or eye-rings. Tail length is c.60% of head-body length, and tail has fur on proximal 5 mm, and naked rest of tail is blackish-brown. Ventral fur is predominately gray, very similar to dorsal fur, and thus does not contrast with it. Fur is short (4-5 mm). Feet are blackish or dark brown, and ears are short and black and appear naked. Female Reig's Opossums probably lack a pouch, but number of mammae has not been reported. Karyotype is unknown.