266 PEOFESSOE OWEN ON CNEMIOENIS. 



flightless bird," and that " it bore nearly the same proportion to the sternum as does the 

 humerus of Notornis." 



As the humerus associated with a nearly entire skeleton of Cnemiornis, discovered by 

 the Hon. Capt. Frazer in the interior of the province of Otago, New Zealand, presents 

 clearly distinctive characters from the one figured in Zool. Trans, vol. v. pi. 66. figs. 

 7-10, I am now disposed to believe that it may prove to be the humerus of an 

 Aptornis, probably Aj^tornis defossor. 



Dr. Hector remarks that, in the humerus of Cnemiornis, " the tuberosity (xi b) repre- 

 senting the pectoral ridge is not so wide " as in that above described and figured by me. 

 I am in some doubt as to the dimension referred to, whether, viz., the " width " of the 

 pectoral process is meant for its basal extent, or the degree in M'hich it projects from 

 such origin. The marked and unequivocal distinction is that, in the humerus of Onemi- 

 omis, of which I have had under inspection a right and left (PI. XXXVIII. figs. 1-6) 

 since the reception of Dr. Hector's Memoir, the pectoral ridge {d) is continued directly 

 from the ecto-tuberosity (outer or radial tuberosity), whereas in AjJtoi'nis (Zool. Trans, 

 vol. v. pi. 66. fig. 7, b') it is divided from that tuberosity (ib. ib.) by a shallow concavity 

 nearly 1 inch in length. 



The ento-tuberosity (inner or ulnar one) in Cnemiornis (PL XXXVIII. figs. 1 & 2, c), 

 instead of rising above the convex articular head (a) of the humerus as in Aptornis (1), 

 does not attain its level ; its expansion below such tuberosity for a pneumatic fossa 

 (fig. 3,p), with its cribriform plate, is a more conspicuous distinction, as Dr. Hector has 

 shown. 



Notwithstanding, however, the several approximations which these characteristics of 

 the humerus of Cneiniornis make to that bone in birds of flight, the almost keelless 

 condition of the sternum, together with the dwarfed proportions of the humerus in 

 comparison with those of the bones of the leg, the pelvis, vertebrae, and skull, confirm 

 the conclusion, in which Dr. Hector accords with myself, that Cnemiornis was unable 

 to fly. 



The existence of the Flightless Duck {Tachyeres brachypterus ; Anas brachyptera, 

 Latham) has long been known ; but the humerus in that species is as long as the tibia, 

 and the power of flight is enjoyed by the young bird, and only lost when the bulk and 

 weight of the adult frame is acquired \ It can hardly be supposed that flight was 

 enjoyed at any age in a lamellirostral palmiped with a humerus of only half the length 

 and less than half the thickness of the tibia. 



It is half an inch less in absolute length than the humerus of Cereopsis ; but the cir- 

 cumference of the shaft is one fourth greater in Cnemiornis (it is 1 inch 6 lines in 

 Cereopsis, 2 inches in Cnemiornis); and the muscular impressions are throughout stronger. 



The groove between the head (PI. XXXVIII. figs. 1-3, a) and the entotuberosity (b) 

 is less deep in Cnemiornis : the pectoral ridge (d) is rather less produced, and is not so 



' As observed by Dr. Cunningham (Zool. Trans, vii. p. 493, pi. 60. fig. 43, humenis ; pi. 62. fig. 62, tibia). 



