I do not know what to call it but it seems Google is testing showing a card or box within the local pack snippets of a specific listing that links you to the business's web site. Jason Parks shared a screen shot of this with me on Twitter, here, look for yourself.
You can see under the Harry S. Cohen listing a card with a favicon and link to the firm's web site. Same with the listing beneath it.
It is not just for professional firms but also landscapers, he shared this screen shot as well:
I cannot replicate this, nor can anyone else I asked. But this is super interesting and in this form, would 100% drive more traffic to the business's web site. Jason posted more screen shots over here.
Forum discussion at Twitter.