P.S. 8/22/2018 - I called Northport’s resident mushroom expert, Ed Reinert, about the fungus, and he asked if I could e-mail him photographs, which I did. Here is his answer to my question:
“Beautiful photos — better than some of the books. The name is Climacodon septentrionale. It is most often found high up on Sugar Maples. It is not a typical shelf mushroom, most of which are in the order Polypore. This is in the Tooth Mushroom order. The common name is just a translation of the scientific name, Northern Tooth.
“You can google it. I am having a hard time fining anyone who has eaten it. I have seen it a couple of times and have a vague memory that it is sour and gooey, not attractive eating, but no reason to think it poisonous. It causes heart rot on live Maples or sometimes Beeches.”
So there we are. I trust Ed’s knowledge, and photos online of Climacodon septentrionale look like what I saw — and what you see above. Now to get word to the people whose trees line that road, as they probably don’t want their maple tree’s heart to rot.