Simplify the following text for a Grade 10 native English-speaking person.
Original: The class is divided into two subclasses : Elasmobranchii ( sharks , rays and skates ) and Holocephali ( chimaeras , sometimes called ghost sharks , which are sometimes separated into their own class ) .
Simplified: They are divided into two subclasses : Elasmobranchii ( sharks , rays and skates ) and Holocephali ( chimaera , sometimes called ghost sharks ) .