18 PROFESSOR OWEN ON THE GENUS DINORNIS. 
skull’, referred in my 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 (Rallide). 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 
Brachypteryz. 
The sternum of the Brachypteryz 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 (Pl. IV. figs. 5 & 6) resembles that of the Brachypterya 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 Brachypterya, 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 Brachypteryz ; the anterior border shows a wide and shallow concavity, not 
the deep narrow median notch. There are no pneumatic fosse 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. pl. 56. fig. 7. 
