356 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 
at the base, less so, however, than in Prothylacynus. Regarding the hind 
limb, two alternatives are possible. Either the tibia was short and the 
back sloped downward from the shoulders, or the hip and shoulder were 
equally elevated. The latter assumption seems preferable and an elon- 
gated tibia and fibula have been supplied, as in Thylacynus. An ossified 
patella has been introduced from analogy with Prothylacynus . The planti- 
grade pose is largely conjectural, as there is no certain means by which 
the gait of an animal may be determined from the skeleton of the fore 
foot alone. It is probable that Prothylacynus , Cladosictis and Amphi- 
proviverra were plantigrade, and, in the absence of evidence to the con- 
trary, the same maybe assumed tentatively for Borhycena. No trace of a 
clavicle is preserved, but one has been inserted from analogy with exist- 
ing carnivorous marsupials. 
Habits. — Some inference regarding the pugnacity of these animals may 
be drawn from the large cicatrice in the mandible of B. tuberata repre- 
sented in fig. 3, PI. XLV. Ability to trail by scent like the Tasmanian 
thylacyne may, perhaps, be inferred from the large olfactory sinuses. The 
blunt claws indicate adaptation to terrestrial progression. The animal 
undoubtedly preyed on the larger placental mammalia. 
BorhyaENA tuberata Ameghino. 
(Plates XL-XLII ; XLV, Figs. 2-6 ; XLVI, Figs. 1 -3a ; LII, Fig. 1 ; LIU, Figs. 2, 2a, 9, 9 a ; 
LIV, Figs. 7, 13; LXI, Fig. 3.) 
Borhycena tuberata Amegh. ; Enum. Sist. Especies Mamif. Fos. Patagonia 
Austral, p. 8, Dec., 1887. 
Borhycena zitteli Amegh.; Enum. Syn. des Especes de Mam. Fos. des 
Formations Eocene de Patagonie, pp. 1 19-120, 1894; Bob Acad. 
Cordoba, p. 375, 1894. 
A nearly complete skull and mandible (No. 15,701) associated with a 
considerable portion of the skeleton, secured by Mr. Peterson eight miles 
south of Coy River, has been identified with this species, which is one of 
the largest of the Santa Cruz thylacynes. 
Apart from characteristic measurements, B. tuberata may be recognized 
by the broad depressed skull, perfectly flat between the orbits, with robust, 
gradually expanding arches. The face is without antorbital constriction. 
The postzygomatic portion of the brain case is considerably elongated and 
