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PATAGONIAN EXPEDITIONS ! PALEONTOLOGY. 
elevation as in Thylacynus , but, unlike that genus, the condylar surfaces 
are wider internally than externally. The angle is broad and strongly 
inflected. The rami are unfused at the symphysis, which extends as far 
back as the anterior border of the posterior premolar. Four or five men- 
tal foramina are present, varying in number and position on opposite 
halves of the same mandible. The most anterior and also the largest of 
these is situated beneath the anterior premolar. 
Cervical Vertebrce . — The atlas and third cervical are associated with 
the skull and feet of a specimen of A. manzaniana (No. 15,154). The 
atlanteal intercentrum (PI. LIII, figs. 1, la) is separately ossified and un- 
fused with the neural arch. The canal for the vertebral artery pierces the 
inner surface of the neural arch above the condyles. A smaller foramen, 
possibly transmitting a recurrent branch of the same artery, penetrates the 
upper surface of the base of the transverse process near its posterior edge. 
The artery emerges on the lower surface of the atlas at the base of the 
transverse process. The neuro-arterial canal is large and widely sepa- 
rated from the upper margin of the cotyles by a broad bar of bone. The 
extremities of the transverse processes are lobate, and the upper surface 
of each is reenforced by a broad median rib. 
The neural spine of the third cervical (PI. LIX, fig. 5) is proportionately 
larger than in Thylacynus. The centrum is strongly keeled inferiorly, 
and the posterior bar of the costal process supports a small diapophysis. 
Appendicular Skeleton. — The humerus of A. manzaniana (PI. LX, 
fig. 4) is without internal epicondylar foramen. The supinator ridge is 
low and does not terminate proximally in a hook-shaped process. The 
deltoid crest is sharper than in Cladosictis or Prothylacynus. 
With the exception of the magnum, the carpus of No. 15,154 is want- 
ing. The magnum resembles that of Borhycena in shape and in the 
arrangement of the facets. The metacarpals (PL LIV, fig. 5) interlock 
proximally to about the same extent as in Sarcophilus. The third and 
fourth are equal in length. The proximal ^articular surfaces are convex 
in dorso-palmar section and concave transversely. The proximal sur- 
face of the fourth is irregularly quadrangular in outline like that of the 
third, instead of triangular, as in Thylacynus and Sarcophilus. The dis- 
tal ends are transversely flattened, with moderately developed keels on the 
palmar surfaces. The metacarpal of the pollex is missing, but from the 
size of the proximal articular surface on the first phalanx of the pollex it 
