PROFESSOR OWEN ON THE GENUS DINORNIS. 251 



of Dinornis didiformis, characterized by superiority of size, or to a distinct species of 

 Dinornis. 



Comparing the femora/ 6,/ 13 (PL XXIII. fig. 1.) and/ 16 {lb. fig. 2.) with each 

 other, it was obvious that one of them differed in its proportions from the rest,/ 13 being 

 relatively thicker, as is shown in the plate and in the table of admeasurements. This 

 femur corresponded much more closely with the femur/ 12 (PI. XXI. fig. 3.) in its general 

 form, its ridges and tuberosities ; but these were less strongly developed, and the manner 

 and extent of abrasion of both proximal and distal articular surfaces would well accord 

 with the supposition of their having been in that cartilaginous or less completely ossified 

 state which characterizes the femur of a bird not quite fully arrived at maturity. The 

 state of development of the muscular ridges and tuberosities forbids the reference of 

 this femur to a very young bird, but supports the conclusion that the bone had belonged 

 to an individual as far advanced in growth as is indicated by the difference in size be- 

 tween it and the femur/ 12. 



The different condition and proportions of the two remaining femora, of 9^ inches in 

 length,/ 6 and/ 16, estabhsh their specific distinctions from the femora/ 13,/ 12 and 

 /2. Of this I think no doubt can be entertained by any anatomical naturalist who 

 may inspect the plate (PI. XXIII.) containing the figures of/ 13 and/ 16, selected for 

 the comparison, or who may give due consideration to the following statement of their 

 differential characters. 



These bones are of equal length but of unequal thickness : the shape of the shaft of 

 the bone is also different ; the relative antero-posterior diameter of/ 13 is much greater 

 than that of/ 16, especially at the proximal end and trochanterial enlargement of the 

 shaft, and just above the inner condyle : the anterior surface of the proximal part of 

 the shaft presents a shallow equable concavity in/ 16 which is not present in/ 13. In 

 /16a pretty sharp ridge leads from the middle of the posterior surface of the shaft ob- 

 liquely to the upper and posterior angle of the inner condyle, and the posterior surface 

 of the expanded shaft above the condyles is regularly excavated by a moderate concavity 

 which is continued uninterruptedly into the inter-condyloid depression. In / 13 an 

 oblong rough tuberosity, with its long axis parallel with that of the bone, exists in the 

 place where we find the oblique ridge in the other bone, the tuberosity being separated 

 from the upper and posterior angle of the inner condyle by a smooth channel or de- 

 pression, which leads to an oval depression much deeper and more circumscribed than 

 is the corresponding concavity in / 16. The complete development of the muscular 

 ridges and tuberosities, with the better preserved state of the articular extremities, show 

 the femur / 16 to be a more mature bone than / 13 ; the differences in proportion and 

 configuration prove it to belong to a distinct species from Dinornis struthoides. 



We next come to the question whether the femora/ 6 and/ 16 belong to the species 

 Dinornis didiformis, founded on the femora/ 7,/ 8,/ 17, the tibia t 3, t 4, t 5, t 8, t 9, 

 t 10, and the metatarsi m 4, m 5 and m 6, and whether the femora/ 6 and/ 16 



VOL. III. PART III. 2 L 



