Crookshanks meows in reply. He doesn't know what kind of potion that Hermione needs to make, and usually avoids the potion classrooms, so doesn't know if there would be a difference if another ingredient was retrieved.

And while he is willing to make a substitution in this case, he just wants to make sure that it would be the right decision.

So he looks up at Jim. Where are these reptilian scales he speaks of? He needs to use his nose to sniff the options.