"Shell seats" refers to seats or chairs that have a curved or contoured backrest and are shaped like a shell, giving them a cozy and comfortable feeling. Full definition
The folding race car shell seats with their high lateral supports and integrated head restraints, together with the two rear seats, provide space for four persons. (ausmotive.com)
Combining contemporary design with practical durability, the resin shell seat can be easily cleaned and maintained, whilst the robust, solid hardwood will stand the test of time. (outandoutoriginal.com)
We found the standard shell seats perfectly comfortable for everyday driving, even after a hundred or so miles behind the wheel. (autoweek.com)