J881.] ANATOMY OF THE JA9ANAS. 645 



The drawing (fig, 2) of the sternum of Metopidius albinucha 

 will show how unlike it is to that of the Rallidse. In the latter 

 group the sternum is always peculiar in that the xiphoid processes 

 exceed in length the body of the sternum, which tapers to a point 

 posteriorly, and from which they are separated by very long and 

 well-marked triangular notches. The carina sterni also is less well 

 developed ; and the clavicles are weaker and straighter, being less 

 convex forwards, than in the Parridse. The sternum and clavicles 



Fig. 2. 



Sternum and shoulder-girdle of Metopidim albinucha, viewed laterally ; 



natural size. 



of Parra and Metopidius in general form, on the other hand, re- 

 semble closely the type found in some of the Pluvialine birds (e. g. 

 Thinocorus, Attagis). 



The pelvis, again, of the Rails presents certain well-marked pecu- 

 liarities. If that of Rallus aquaticus be taken as a typical form 

 it will be found that the ilia are long and narrow, and but little ex- 

 panded in their preacetabular part. The postacetabular portion of 

 the pelvis is but little bent down on the preacetabular part ; and the 

 ischia and pubes are but little everted. The ischia are united by 

 broad bony plates to about the three most posterior "sacral" ver- 

 tebrae ; between these plates and the expanded part of the ilia above 

 are well-developed and deep fossae, 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 from just behind the anti- 

 trochanteric 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 there- 

 fore 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 Parra and Metopidius ' the ilia are wider and more expanded 

 * Milne-Edwards has also described the difference of the pelvis in the Jacjanas 

 as compared with that of the true BnlUdss : cf. ' Oiseavu Fossiles,' ii. p. 123. 



