A new fossil marine diatom resting spore morpho-genus Gemellodiscus Suto gen. nov. is described using samples from DSDP Site 338 in the Norwegian Sea, Sites 436 and 438 in the northwest Pacific and the onland Newport Beach Section, California. Gemellodiscus is characterized by possessing a valve with setae of several types: bifurcated seta, fused seta and crossed seta. Eleven taxa are described and their stratigraphic ranges are presented: G. incurvus (Bailey) Suto comb. nov., G. pliocenus (Brun) Suto comb. nov., G. cingulus Suto var. cingulus sp. nov., G. cingulus var. longus Suto var. nov., G. bifurcus Suto sp. nov., G. hirtus Suto sp. nov., G. caveatus Suto sp. nov., G. micronodosus Suto sp. nov., G. dicollinus Suto sp. nov., G. geminus Suto sp. nov. and G. dimontanus Suto sp. nov.