112 NATURAL HISTORY OF KEEGUELEN ISLAND. 



the costal processes, the development of the keel relative to the size of 

 the body of the boue, the general disposition of the coraco-sternal aztic- 

 ulation, and the doubly-notched posterior border, are all thoroughly 

 gull-like. The point of difference of this sternum from that of the gulls, 

 is a moderate rounding of its posterior margin, so that the outer of the 

 two spurs of bone does not reach so far back as the inner ; the reverse 

 beiug the case in Laridce. Such form of the posterior margin is a com- 

 mon grallatorial character ; nevertheless, in itmosa, for instance, this 

 border is perfectly transverse. Moreover, the difference between CM- 

 onis and Larus in this respect is less than the difference between Larus 

 and its near neighbor Lestris. In the wading birds the manubrium is 

 either absent or quite small, the keel is very deep in proportion to the 

 extent of the body, and the body is compressed anteriorly, and very 

 deeply hollowed. As to all of these features, the sternum of Chionis 

 differs from that of the plovers and approaches that of the gulls. In 

 comparison with either plovers or gulls, there is a feature peculiar to 

 Chionis in the relation borne by the furculum to the sternum. For 

 both gulls and plovers have a strongly bent furculum with a well devel- 

 oped posterior spine reaching nearly to the apex of the sternal keel ; 

 whereas, in Chionis the furculum is scarcely bent, has no spine what- 

 ever, and its apex is closer to the manubrium than to the sternal keel. 

 In place of a posterior spine there is a slight process of bone directly 

 facing the manubrium. 



The clue to the true affinity of the bird furnished by these gull-like 

 sternal characters, is traceable in every part of the skeleton. 



To begin with the skull. The Gallince may be at once thrown out of 

 the discussion by the absence in Chionis of the following, among other, 

 distinctively " alectoromorphic^^ features.* The occipital condyle is sim- 

 ple, not notched ; there are no basipterygoid facets, the pterygoids 

 articulating with the basisphenoid only at their extremities; the in- 

 ternal lamellte of the palatine bone are strongly developed instead of 

 rudimentary ; and the shape of the palatines, as a whole, is radically 

 diffVirent. The maxillopalatines are long and spongy, instead of being 

 lamell<ir. Vomer is large, conspicuous, and completely anchylosed with 

 the palatines. The articulation of the quadrate bone with the temporal 

 is very different, nor is there in front of this boue the immense fenes- 

 trated process so conspicuous in Gallince. The angle of the mandible is 

 not strongly upcurved. There are great pits on top of the skull for the 



* Huxley on Classification, P. Z. S. 1867, p. 450. 



