Most probably they are palm fruits.

Sir, do you have any pics of the mother plant(source)?  And what is the size of those seeds?

Either they are fruits of Magnolia species or can be cones of some gymnosprm species

Calamari fruits

these might be edible 

Buriti or Miriti ( Scientific name: Mauritia flexuosa)

It is a palm tree widely distribute in flooded or swamp areas of Cerrados (savana-like ecosystem) from South America. The tree can reach up to 30 meters. The plant bloos almos all year round, but especially from April to August.

Please try in genus Calamus. 

Try Raphia genus

I agree with Nzigidahera Benoit. These fruits are of Raffia palm.

From where you have collected this fruit?

Cane

calamus genus

Dr. Goyal,

The fruits depicted in the photograph are undoubtedly rattan (cane) palm seeds. If you could give me the seed dimensions, possibly I could suggest a taxon name.

With regards,

Ankur J Saikia

Dear peers,

Thanks for your suggestions. I met these seed in a local market in Singtam (Sikkim). These are edible and once the cover is removed these are like areca nut. Sorry i don't have the plant source.

Dr. Goyal,

As per your recent statement, yes, they are undoubtedly rattan (cane) palm seeds. Data on seed dimensions could have helped in ascertaining whether it is Calamus sp. or Plectocomia sp.

With regards,

Ankur J Saikia

Yes, it is rattan palm fruit. In Bangladesh it is called bet fal. 

could be Raphia taedigera