(syn. Aythya Ϯ Ring-necked Duck A. collaris) Gr. περισσος perissos wonderful; νηττα nētta duck; "Perissonetta, gen. nov. 1 Diagnosis.— Similar to Nyroca, but length of exposed culmen equal to length of inner toe with claw (instead of decidedly shorter); feathering on sides of maxilla extending forward as far as the feathering at the base of the culmen; anterior outline of feathering at the base of culmen broadly convex; and length of wing only about 4 times the length of exposed culmen. ... Type. — Anas collaris Donovan. ... As the characters that we have above given show, this species forms one of the most trenchantly distinct groups among the genera allied to Nyroca. ... 1 perissós, mirabilis; nētta, anas." (Oberholser 1921).