SINCLAIR ! MARSUPIALIA OF THE SANTA CRUZ BEDS. 
425 
PALjEO thentinap . 
PALCEOTHENTES (Moreno) Ameghino. 
(Plates LXIII, Figs. 1-7 ; LXIV, Figs. 1-2 ; Text Fig. 8.) 
Palceotenthes Moreno ; Patagonia, Resto de un Continente hoy sub- 
mergido, p. 22, 1882 ( nomen nudum). 
Palceothentes (Moreno) Amegh.; Enum. Sist. Especies Mamif. Fos. Pat. 
Aust., p. 5, 1887. 
Palceothentes Lydekker; Zool. Record for 1887, XXIV, Mamm., 54, 
1888. 
Epanorthus Amegh.; Contrib. al Conoc. Mamif. F6s. Rep. Argent., pp. 
271-272, 1889. 
Metaepanorthus Amegh.; Enum. Syn., p. 92, 1894. 
Paraepanorthus Amegh.; Enum. Syn., pp. 93-94, 1894. 
This is the most abundant and best known of the Santa Cruz diproto- 
donts, at least four species being represented in the collections at Prince- 
ton University and the American Museum of Natural History. 
Dentition (Pis. LXIII, figs. 1-7; LXIV, figs. 1-2). — The dental for- 
mula in Palceothentes is \. Three upper incisors are figured by Ame- 
ghino (1895, p. 96, fig. 76 ; 1903, p. 14 1, fig. 62, p. 170, fig. 95) for P. 
minutus. The premaxillary region has been broken from the only skull 
in the Princeton collection (No. 15,225) and the incisor formula cannot be 
verified. The canine has also been broken in this specimen. From the 
cross-section of the root it appears to have been considerably flattened 
laterally. The premolar-molar series forms a crescent, tapering in width 
at both ends, with the convexity directed outward. The three upper pre- 
molars may be either closely crowded (P. intermedins , PI. LXIV, fig. 1) 
or moderately spaced (P. aratce , PI. LXIII, fig. 2d). The anterior pre- 
molar is single-rooted in the latter species, double-rooted in P. interme- 
dins. The tooth has been shed in the only specimen of P. aratce in the 
collection (No. 9549* Am. Museum) and in the skull of P. intermedins 
has been considerably damaged. The median premolar is laterally com- 
pressed, with a central cusp and well marked anterior and posterior acces- 
sory cuspules. The posterior premolar is a smooth trenchant blade, 
greatly widened posteriorly and tapering to an edge in front, where a 
