Euamyda Stejneger, Bull. Mus. Comp. Zool., 94:7, 9, 12, 1944; new (substitute) name for Amyda mutica of Agassiz (1857:399); type, Amyda mutica Agassiz by monotypy.
Type Species.—Trionyx aegyptiacus (= Testudo triunguis Forskål).
Diagnosis.—Cutaneous femoral valves absent; width of postorbital arch of skull less than diameter of orbit; pterygoids usually not contacting opisthotics; carapace lacking prenuchal bone and marginal ossifications; nuchal bone lacking conspicuous ventral ridges; posterior margin of nuchal overlying first pair of pleurals; lateral parts of nuchal bone overlying second pair of ribs; neurals seven or eight, rarely six or nine; pleurals seven or eight pairs, posterior one or two pairs sometimes in contact medially; distinct suture usually present between hyoplastra and hypoplastra; most laterad prong of posteromedial process of hypoplastra inserted between bifid anterolateral process of xiphiplastra.
Synonomy.—Geoffroy published a synopsis of the species he recognized (1809) prior to his formal description of the genus Trionyx (1809a). Schweigger, nevertheless, probably was the first person to recognize the soft-shelled turtles as a distinct group, and he proposed for it the name Amyda in an unpublished manuscript that he sent to Geoffroy. The latter author (1809a:15) relegated the name Amyda to the synonomy of Trionyx javanicus by means of the following entry: "Amyda javanica. Schweigger, dans un manuscript communique a l'Institut." Stejneger (1944:7) maintained that this publication of Schweigger's monotypic generic name clearly established its availability for the species congeneric with Amyda javanica (= Testudo cartilaginea Boddaert, 1770). Loveridge and Williams (1957:422) contend that this mere mention of the name Amyda neither constitutes the proposal of a new name nor validates it, and that the first valid usage of the name Amyda is that of Fitzinger (1835:120), who later (1843:30) designated the type species as Amyda subplana. The name Amyda cannot date from Oken (1816:348) as Volume 3 [Zoologie] of his Lehrbuch der Naturgeschichte published in 1815-1816 has been placed on the Official Index of Rejected and Invalid Works in Zoological Nomenclature with the Title No. 33; see Opinion 417 (Hemming, 1956).
There has been considerable debate as to whether Geoffroy did or did not designate a type species of the genus Trionyx (1809a). Although not specifically designated as the type species, Trionyx aegyptiacus (= Testudo triunguis Forskål) is considered by Smith (1930:2), Schmidt (1953:108, footnote), and Loveridge and Williams (1957:422) to have been sufficiently indicated by Geoffroy as the type species. But Stejneger (1944:6), H. M. [445] Smith (1947:122), Conant and Goin (1948:11), and Mertens and Wermuth (1955) maintained that Geoffroy did not adequately designate a type species, and that Fitzinger (1843:30) designated the type species as Trionyx granosus (= Lissemys punctata), a synonym of Geoffroy's species, coromandelicus.
If Fitzinger's designation of a type species is accepted, the name Trionyx is applicable to the forms herein referred to Lissemys, and Amyda to the American forms. If Geoffroy's designation is accepted, the American forms are referable to Trionyx, and Amyda is a synonym.
The preceding includes only those generic names (listed in chronological order) that have been applied to Recent American soft-shelled turtles. Generic synonyms of the genus Trionyx applicable to Old World species are listed by Stejneger (1907:514), Smith (1931:165), and Loveridge and Williams (1957:420-21).
Trionyx is the most widespread genus of the family; most of the species occur in southeastern Asia. All North American soft-shelled turtles belong to this genus.
For quick reference, all the specific and subspecific names proposed for soft-shelled turtles in North America are listed below in alphabetical order (left hand column) with their nomenclatural status as recognized in this paper. The synonyms are listed in the account of the appropriate species or subspecies, and are discussed under the subsection entitled "Remarks."
| agassizi | Trionyx | spinifer asper |
| annulifer | Trionyx | spinifer spinifer |
| argus | Trionyx | spinifer spinifer |
| asper | Trionyx | spinifer asper |
| ater | Trionyx | ater |
| bartrami | Trionyx | ferox |
| emoryi | Trionyx | spinifer emoryi |
| calvatus | Trionyx | muticus calvatus |
| ferox | Trionyx | ferox |
| georgianus | Trionyx | ferox |
| georgicus | Trionyx | ferox |
| harlani | Trionyx | ferox |
| hartwegi | Trionyx | spinifer hartwegi |
| hudsonica | Trionyx | spinifer spinifer |
| mollis | Trionyx | ferox |
| microcephalus | Trionyx | muticus muticus |
| muticus | Trionyx | muticus muticus |
| nuchalis | Trionyx | spinifer spinifer |
| ocellatus | Trionyx | spinifer spinifer |
| olivaceus | Trionyx | spinifer spinifer |
| spiniferus | Trionyx | spinifer spinifer |