139 



TRIBONYX ROBERTI ANDREWS. 



Tribonyx roberti Andrews, Ibis 1897, p. 356, pi. 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 



Least width of acetabular region of Pelvis 

 Width at Antitrochanter .... 

 Width at anterior angle of Pelvic Escutcheon . 

 Width at Posterior angle of Pelvic Escutcheon. 

 Length of Sacrum .... 



Tibia. 



Length 143 mm. 



Width at distal extremity 12 ,, 



Width at middle of shaft 7 „ 



82 mm. approx. 



14 „ 



40 „ 



36 „ 



40 „ 



68 „ 



Femur. 



Length 



Width at distal extremity 



Width at middle of shaft 



Habitat : Sirabe in C. Madagascar. 



83 mm. 

 17 „ 

 7 „ 



