18 PROFESSOR OWEN ON THE GENUS DINORNIS. 



skull', referred in ray Memoir of 1848 to the genus Notornis, has belonged ; and although 

 its shape, so far as I at present know, is unique in the class of Birds, I conceive it to be 

 a modification of that type which characterises the Rail and Coot tribe {Rallidce). The 

 grounds for this opinion will, perhaps, be best illustrated if I premise a description of 

 the sternum of that existing species of the family in New Zealand, which, being 

 incapable of flight from the shortness of its wings, I have referred to a genus called 

 Brachypteryx. 



The sternum of the Brachypteryx is almost as remarkable for its narrowness as in the 

 Apteryx for its breadth. The anterior border has a deep rounded median emargination, 

 between the projecting borders of which, and the more produced costal angles, the wide 

 coracoid grooves are placed. The costal border occupies one-fifth of the lateral margin 

 of the sternum and presents articulations for five sternal ribs : the narrow posterior 

 border has a deep and moderately wide median emargination and two lateral, very narrow 

 and very deep ones, like fissures, equaling one-third of the entire length of the sternum, 

 the outer border of each fissure being a long slender filiform process. Two ridges com- 

 mencing on the outer surface of the sternum behind the coracoid grooves, converge to 

 support the fore part of a shallow keel which subsides before it reaches the posterior 

 border of the sternum. The outer surface of the bone is slightly concave between the 

 keel and the costal margins of the bone. The upper or concave surface of the sternum 

 presents two pneumatic depressions behind the coracoid grooves. 



The sternum of the Notornis (PI. IV. figs. 5 & 6) resembles that of the Brachypteryx in 

 its elongated and narrow proportions, and in the rudiment of a keel which commences 

 by two ridges converging from the inner ends of the coracoid grooves : but the lateral 

 styliform appendages, and consequently the lateral fissures of the posterior part of the 

 bone, are wholly wanting, and the intermediate part of the body of the bone is narrower, 

 and gradually contracts to what seems to have been an obtusely pointed extremity : but 

 this is broken in the specimen. The keel does not project so far from the surface of 

 the bone as in the Brachypteryx. The coracoid grooves are more shallow, and the whole 

 sternum, although its general form and proportions are indicative of a bird of the same 

 natural family as the Brachypteryx, shows that the wings were still less developed than in 

 that genus. The costal border exhibits articulations for five sternal ribs (fig. 7) on each 

 side, as in the Brachypteryx ; the anterior border shows a wide and shallow concavity, not 

 the deep narrow median notch. There are no pneumatic fossae on the upper surface. 

 The anterior buttresses of the keel divide the fore part of the anterior surface of the 

 sternum into three parts, as shown in fig. 8, where the coracoid grooves are represented 

 near the fractured anterior or costal angles of the bone. 



' Zool. Trans, iii. p. 366. pi. 56. fig. 7. 



