See the main Ephoron page for details about this species, which is not known to differ in any important ways (besides location) from the other species.
On page 243 of Hatches II there is a passage from an 1802 speech before the American Philosophical Society in which this mayfly was introduced to science. It was the first mayfly species described in the United States, so it is ironic that it went unnoticed through so many of the early decades of our sport.