Page:Rothschild Extinct Birds.djvu/173

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139



TRIBONYX ROBERTIANDREWS.

Tribonyx roberti Andrews, Ibis 1897, p. 356, pl. IX, figs 4-7.

This bird is described from an imperfect pelvis, a perfect left tibio-tarsus and a femur. The pelvis differs from that of T. mortieri in not having the deep depression in the ilia in front of the acetabulum and above the pectineal process. It also differs in having a rather wider pelvic escutcheon and wider renal fossal, and the supra-acetabular ridges of the ilia are smaller than in the Australian bird. The beautifully-preserved left tibia differs from that of T. mortieri in having the intercondylar groove wider and shallower, the inner condyle less massive, thus making the difference between the inner and outer condyle more marked; T. roberti also has the shaft immediately above the extensor bridge wider, the bridge itself less oblique, and the fibular crest is longer.

The measurements are:—

Pelvis.
Length of Ilium 82 mm. approx.
Least width of acetabular region of Pelvis 14 "
Width at Antitrochanter 40 "
Width at anterior angle of Pelvic Escutcheon 36 "
Width at Posterior angle of Pelvic Escutcheon 40 "
Length of Sacrum 68 "
Tibia.
Length 143 mm.
Width at distal extremity 12 "
Width at middle of shaft 7 "
Femur.
Length 83 mm.
Width at distal extremity 17 "
Width at middle of shaft 7 "

Habitat: Sirabé in C. Madagascar.