is the correct gender combination.

Thanks - can you provide a published reference for this change?

Leave it to European taxonomists to stir the status quo. In this case they returned to the genus treatment accepted earlier by Casey (1918:p164). I suspect that Deuve (1998) is responsible for the "earliest recent" retroversion to genus Amerizus. The full reference is cited in a related article by Sciaky & Toledano (2007). Amerizus is fundamentally separated from Bembidion on the basis of a unique walnut-shaped sclerite present inside the endophallus. Amerizus was also given genus rank in Nomina Carabidarum by Lorenz (2005).

Do you mean the genus can't be keyed out without dissections, and only males can be keyed to genus? Or one has to key to species first in order to know what genus they belong to? Sounds like it should have been kept a subgenus to me!

of course traces a path of external features in a key to the subgenera of Bembidion published in American Beetles (2001). But that artificial key was written for the North American members in mind. It might not work for the World fauna in the case of "Amerzus". I just don't know. When considering the World fauna, apparently certain European taxonomists felt strongly enough about the unique endophallic sclerite to warrant separate genus status. In general, nomenclature presented as genus vs subgenus appears to be in constant state of flux as fueled by the latest authoritative publication. For example, I have no trouble still accepting "subgenus Amerizus" by Yves Bousquet in his Illustrated Identification Guide to Northeastern North American Ground Beetles (2010). I would be curious to learn if, at the worldwide level, a unique set of external features correlates one-to-one with the unique endophallic sclerite.