489 INDEX GENERUM MAMMALIUM. 
Orthocynodon-— Continued. 
Orthocynodon: ópfióz, straight; «ocv, dog; 65@v=66o0vs, tooth—in allusion to 
the canine, in contrast with that of Amunodon. 
Orthodolops AwEcGniNo, 1903. Allotheria, Polydolopid:e. 
Anales Mus. Nac. Buenos Aires, IX (ser. 3*, II), 130-131, 148, 177, figs. 54, 106, 
July 18, 1908. 
Type: Orthodolops sciurinus Ameghino, from the Notostylops beds of Patagonia. 
Extinct. Based on the last two right, lower molars. 
Orthodolops: ópfiós, straight; + (Poly-)dolops. 
Orthodon HRarixEsqvE, 1815. Cete, Physeteridze. 
Analyse de la Nature, 60, 1815 (nomen nudum); Gmav, Cat. Seals & Whales 
Brit. Mus., 210, 1866 (synonym of Physeter). 
Type: Physeter sp. (‘Orthodon R. sp. do’ [= espéce du genre précédent, PAyseter]). 
Orthodon: ópfós, straight; 66@v=ddovs, tooth. 
Orthogeniops AmEGHINO, 1902. Tillodontia, Nostostylopidee. 
Bol. Acad. Nac. Cien. Córdoba, XVII, 33, May, 1902 (sep. p. 31). 
New name for Orthogeniwm Roth, 1901, which is preoccupied by Orthogenium 
Chaudoir, 1855, a genus of Coleoptera. 
Extinct. 
Orthogeniops: Orthogeniwm; Ow, aspect. 
Orthogenium Rorn, 1901. Tillodontia, Notostylopide. 
Revista Mus. La Plata, X, 255, Oct., 1901 (sep. p. 7). 
Type: Orthogenium ameghinoi Roth, from the lower Tertiary of Patagonia. 
Name preoccupied by Orthogenium Chaudoir, 1835, a genus of Coleoptera. 
Replaced by Orthogeniops Ameghino, 1902. 
Extinct. 
Orthogenium: Ópfós, straight; y éveiov, chin, jaw. 
Orthogeomys Merriam, 1895. Glires, Geomyidee. 
N. Am. Fauna, No. 8, pp. 23, 26, 172-179, pl. 19 figs. 1-2, text figs. 60-64, 
maps 3, 5, Jan. 51, 1895. 
Type: Geomys scalops Thomas, from Tehuantepec, Mexico. 
Orthogeomys: 6p90s, straight; -- Geomys—in allusion to the unusual shape of the 
skull, which is much elongated, with broad, flat frontals. 
Ortholophodon Rorn, 1901. Ungulata, Ancylopoda n 
Revista Mus. La Plata, X, 253, Oct., 1901 (sep. p. 5). 
Type: Ortholophodon prolongus Roth, from the upper ‘Cretaceous’ of Lago Mus- 
ters, Territory of Chubut, Patagonia. 
Extinct. 
Ortholophodon: ópfiós, straight; Ad@os, crest; 65@v=ddo0vs, tooth—probably in 
allusion to the median crest of the premolars. 
Orthomyctera AMEGHINO, 1889. Glires, Caviidee. 
Cont. Conocimiento Mamif. Fósil. Repub. Argentina, in Act. Acad. Nac. Cien., 
Córdoba, VI, 218-221, pls. x1 figs. 4-7, x11 fig. 1, 1889. 
Ortomyctera LYDEKKER, Zool. Record for 1891, XXVIII, Mamm., p. 34, 1892. 
Species, 4: Cavia rigens Ameghino, Orthomyctera vaga. Ameghino, Dolichotis lacu- 
nost Ameghino, from the Araucanian formation (Miocene), of Monte Her- 
moso near Bahia Blanca; and Orthomyctera lata Ameghino, from the Pampean 
iormation (Pliocene), in the vicinity of Córdoba, Argentina. 
Extinct. 
Orthomyctera: ópfós, straight; jvicr7)p, nose—*'la apertura nasal posterior colo- 
cada más atrás y mucho más angosta que en Dolichotis." (AMEGHINO.) 
Orthomys AmEGHINO, 1881. Glires, Octodontide. 
* La Antigüedad del Hombre en el Plata, II, 306, 1881;’’ Act. Acad. Nac. Cien., 
Córdoba, VI, 150-151, 902, pls. vir fig. 6, xxv figs. 10, 13, rxxir fig. 19, 1889. 
Type: Orthomys dentatus Ameghino, from the Rio de La Plata; subsequently 
Iound in the barrancas near Paraná, Argentina. 
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