Simplify the following text for a Grade 10 native English-speaking person.
Original: Elasmobranchii is a subclass of Chondrichthyes or cartilaginous fish , that includes the sharks ( Selachii ) and the rays and skates ( Batoidea ) .
Simplified: Elasmobranchii is a subclass of Chondrichthyes or cartilaginous fish , that includes the sharks and the rays and skates .