A comparative analysis of type material of nongeniculate coralline red algae (Corallinales, Rhodophyta) associated with the Siboga Expedition (1899-1900) to the Malay Archipelago and lodged in L and TRH has been undertaken. Of the 23 species and infraspecific taxa involved, 5 are based on holotype collections, 3 were properly lectotypified by previous authors, and 15 are properly lectotypified here. L contains 5 holotypes, no holotype fragments, 13 lectotypes, and no lectotype fragments while TRH contains no holotypes, 5 holotype fragments, 5 lectotypes, and 6 lectotype fragments. Lithothamnion siamense is correctly lectotypified with material from the Gulf of Thailand and not from Siboga material, and a new lectotype with conceptacles is proposed to supersede the existing sterile lectotype of Archaeolithothamnion timorense. Isolectotypes and paratypes at L and TRH have been identified and marked, and information on the basionym, nature, extent, and location of type material, type locality and collection data, and references to published illustrations of type material have been provided for all species and infraspecific taxa. Brief comments on five rejected forma names are included.