I rediagnose the microhylid frog Callulops robustus (Boulenger) based on examination of the type series and recently collected topotypic material. The species is distinguished by its large size, narrowly expanded finger and toe discs lacking or with poorly developed circum-marginal grooves, pustulose dorsal skin, long snout, unpatterned orange-brown or reddish-brown dorsal coloration, and uniformly brown ventral coloration. The species is almost certainly restricted to the type locality, Misima Island, at the easternmost extremity of the geographic range of Callulops. Based on examination of the holotype and recently collected material from the general area of the type locality, I then rediagnose Mantophryne microtis Werner and remove it from synonymy with C. robustus. It is readily distinguished from the latter species by its somewhat smaller body size, well-developed circum-marginal grooves on at least some of the fingers and toes, short snout, and color pattern of tiny white flecks on a dark gray or black ground color. This species is currently known from mountain ranges on the northeastern coast of New Guinea, but it may prove to occur in similar North Coast ranges farther to the west. I also discuss the taxonomic status of Pomatops valvifera Barbour and Liophryne kampeni Boulenger, currently placed in synonymy with C. robustus. Both species are clearly not referable to C. robustus, but each is known only from single, faded specimens, and compelling rediagnosis of each awaits collection of fresh topotypic material.