Carinate Birds from Central Madagascar. 



357 



A beautifully-preserved left tibia (PI. IX. fig, 6) possibly 

 belongs to tliis species, since it is closely similar to that of 

 Tribomjx mortieri. It differs, however_, in the following 

 points : — (1) The intercondylar groove is a little wider and 

 shallower ; (2) the inner condyle is less massive, so that the 

 difference between the inner and outer condyles is more 

 marked than in the Australian bird; (3) the shaft imme- 

 diately above the extensor bridge is wider, and the bridge 

 itself less oblique ; (4) the fibular crest is relatively longer. 

 It also, in most respects, resembles the tibia of Porphyria, 

 but is distinguished from it by the relatively larger size of 

 the articular ends, the more marked inflection of the distal 

 one, and the fibular crest is longer. The til)ia of Ocydromus 

 is much stouter and has a less incurved distal end than the 

 fossil, which, in this respect, as well as in some other points, 

 closely approaches the Fulicine type. 



The dimensions of this tibia and of those of some other 

 Rails are given below : — 



