Okay so if Vastra is a Silurian and more reptile-like than mammal-like, consider:

  • Vastra grabbing bugs of the sill with her tongue when no-one’s looking
  • Vastra sunning naked as the day she was hatched in her conservatory
  • Vastra seeking out small, dark places when worried
  • Vastra becoming embarrassingly cuddly when the chill of Victorian London gets to her