[Pharo-project] Class and Metaclass explanation in PBE

Hi folks. I was reading chapter 13 of PBE and there is something I don't understand. In page 283 it says: "Every metaclass is-a class, hence inherits from Class. Class in turn inherits from its superclasses, ClassDescription and Behavior." page 278, rule 8, it says: "Every metaclass inherits from Class and Behavior." However, if I open a class browser, I see that Metaclass inherits from ClassDescription, not Class. So, I don't understand :( Can anyone clarify me this? Thanks Mariano