361 



Dinornis didiformis ; showing the great thickness of the compact walls 

 at the middle of the shaft. 



1581. The right tibia of the Dinornis didiformis. 



1582. The half of the shaft of the right tibia, longitudinally bisected, of the 



Dinornis didiformis. 



1583. The left tibia of the Dinornis didiformis. 



1584. A portion of the shaft of the left tibia of the Dinornis didiformis. 



The length of the tibia No. 1581 is fifteen inches and a half, that of the 

 tibia No. 1583 is sixteen inches and a quarter; the circumference at the 

 middle of the shaft is four inches in the first, and four inches one line in 

 the second : they both clearly belong to the same species and manifest the 

 same proportions to the femora Nos. 1577 and 1578, as the tibia No. 

 1570 does to the femur No. 1569. The tibia of the Dinornis didiformis 

 is thicker in proportion to its length, has relatively broader proximal and 

 distal extremities, and a longer ridge for the attachment of the fibula, 

 than that of the Dinornis giganteus or Din. ingens. 



The anterior ridge at the proximal end of the bone is nearer the middle 

 in Din. didiformis, the interspace between that and the external ridge 

 being of the same breadth in the tibiae of the small and large species, 

 notwithstanding the difference of total breadth. The external proximal 

 ridge curves more abruptly outwards from the shaft of the bone in the 

 small than in the large tibia?, whereas the contrary character ought to 

 have been manifested if the difference of size had depended on difference 

 of age, such muscular ridges being more strongly produced in old than 

 in young birds. The shaft of the bone is flatter antero-posteriorly, com- 

 pared with its breadth, in the small than in the large tibia, and is more 

 nearly trihedral, owing to the greater flatness of the inner and anterior 

 surface and the less rounding off of the inner margin. 



1585. The left tarso-metatarsal bone of the Dinornis didiformis. This bone 



measures six inches ten lines in length, three inches three lines in cir- 

 cumference at the middle of the shaft, and three inches in breadth 

 across the distal end. If these dimensions be compared with those of 



3 a 



