The specific name psix is not a spelling error, but is the greek word psix, meaning crumb.  This alludes to the fragmentray nature of the type materials.

Nannococcyx psix
Olson   1975
Holocene of St. Helena, south Atlantic Ocean
Primary materials: Holotype: right humerus

Storrs L. Olson,
Paleornithology of St. Helena Island, south Atlantic Ocean
Smithsonian Contributions to Paleobiology 23 (1975)

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Coua primaeva
Milne-Edwards & Grandidier   1895
Holocene of Madagascar
Primary materials: Type: Tarsometatarsus

Kālmān Lambrecht,
Handbuch der Palaeornithologie
1024 p. (1933)
Gebrüder Borntraeger, Berlin

See also:
Pierce Brodkorb,
Catalogue of fossil birds. Part 4 (Columbiformes through Piciformes)
Bulletin of the Florida State Museum, Biological Sciences 15 (1971): 163-266

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Coua berthae
Goodman & Ravoavy   1993
Holocene of Madagascar
Primary materials: Holotype: left half of the pelvis

Steven M. Goodman & Florent Ravoavy,
Identification of bird subfossils from cave surface deposits at Ahjohibe, Madagascar, with a description of a new giant Coua (Cuculidae: Couinae)
Proceedings of the Biological Society of Washington 106 (1993): 24-33

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