POSITION OF THE JAANAS. 227 



are but little everted. The ischia are united by broad bony plates to p - Z ' 6 ^ 5 1881 ' 



about the three most posterior " sacral " vertebra ; between these plates 



and the expanded part of the ilia above are well-developed and deep 



fossa?, occupied, in the fresh state, by the posterior portion of the 



kidneys. Viewed from above, the well-marked " postacetabular " ridge, 



which divides off the dorsal from the lateral aspect of the pelvis, running 



Fig. 2. 



Sternum and shoulder-girdle of Metopidius albmucha, viewed laterally ; 

 natural size. 



from just behind the antitrochanteric eminence to the posterior spine of 

 the ilium, presents, a little behind those two points, a strongly projecting 

 process. The greatest breadth of the postacetabular part of the pelvis is 

 therefore here, and not at the more anteriorly-situated prominence, close 

 to the antitrochanter. Viewed from the side, this ridge forms a sort of 

 overlapping roof to the slightly excavated external pelvic fossa. The 

 genera Ocydromus, Aramides, Fulica, and Porphyrio do not essentially 

 depart from this type. 



In Parr a and Metopidius* the ilia are wider and more expanded 

 anteriorly. The postacetabular ridge has hardly any median projection ; P. Z. S. 1881, 

 and the pelvis is widest, dorsally, just behind the antitrochanter s. The P* ^* 

 plates of bone between the ischia and sacrum are narrower, and the 

 posterior part of the renal fosssD less well developed, and more open, in 

 consequence. In all these points these forms thus approach the Limi- 

 coline birds. 



There is one other point of interest in the osteology of the Parridse. 

 This is the extraordinary form assumed by the radius in some of tha 

 genera. In birds, as a rule, the ulna is -a stouter bone than the radius, 

 this last being almost universally a slender cylindrical bone. In Meto- 

 pidius africanus, as already noticed by M. A.Milne-Edwards t, as well as 



* Milne-Edwards has also described tke difference of the pelvis in the Jasanas as 

 compared with that of the true Ballidse : cf, ' Oiseaux Fossiles,' ii. p. 123. 

 t ' Oiseaux Fossiles,' ii. p. 134. 



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