Snape wears robes that have special sleeves that flare out a lot at the arms and are split up to the shoulder. Use the How-To Slytherin Robes tutorial available on about.com in their DIY Fashion ...

We know from Slughorn that both Lily and Snape excelled at potions, so, mudblood or not, Severus would undoubtedly hold much respect for her abilities and have something in common with her.