The concave inner surface of the umbrella of a jellyfish or other medusa.
- ‘These rhopalial ganglia presumably sort this information and then distribute it to the appropriate effectors, the swim musculature, via the distributed nerve net of the subumbrella.’
- ‘From the center of the subumbrella hangs the manubrium, which terminates with a mouth opening.’
- ‘Hydromedusae swim by rhythmically contracting the circular swimming muscles located in the subumbrella.’
- ‘The base of the manubrium appears as a dark square in the center of the subumbrella.’