Fabaceous fruit Derrisocarpon miocenicum gen.et sp.nov. and leaflet Derrisophyllum siwalicum gen.et sp. nov., comparable to modern Derris trifoliata Lour., are recorded from the sub-Himalayan Lower Siwalik deposits (Middle Miocene) of Darjeeling foothills, West Bengal, India. Derris trifoliata and all other extant species of the genus are distributed in the tropical, humid areas of the Indian subcontinent, eastern part of Africa, Madagascar, South East Asia and northern Australia. Fossil remains of Derris species till date are reported from the Eocene to Holocene sediments exposed in the eastern part of India only. Site of origin of the Derris species in the eastern part of India may be suggested considering the restricted occurrence of the fossil remains. Derrisocarpon miocenicum and Derrisophyllum siwalicum are recorded from the Siwalik sediments that has records of a large numbers of fossil fabaceous taxa of tropical, humid environment. Derris trifoliata, to which Derrisocarpon miocenicum and Derrisophyllum siwalicum resemble closely, is a frequent component of the modern back mangrove swamps. All these evidences suggest a tropical, humid environment of deposition of the sediments recovering the fossil Derris fruit and foliage viz., Derrisocarpon miocenicum and Derrisophyllum siwalicum.