"...one or both webs may be so deeply incised, that is, cut away, that the palmation is practically reduced to semipalmation, as in terns of the genus Hydrochelidon." Elliot Coues, 1884

Incised Webbed Foot of a Tern

"...one or both webs may be so deeply incised, that is, cut away, that the palmation is practically…