359 



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 depression, which leads to an oval 

 depression much deeper and more circumscribed than is the corresponding 

 concavity in the present femur. The complete development of the 

 muscular ridges and tuberosities, and the better preserved state of the 

 articular extremities, show this femur to be a more mature bone than 

 No. 1573 ; the differences in proportion and configuration prove it to 

 belong to a distinct species from Dinornis strut hoides. 



1576. The shaft of the left femur of a younger individual of the Dinornis 

 dromioides. 



\b77- The right femur of the Dinornis didiformis, Owen. 



1578. The left femur of the Dinornis didiformis. This bone is eight inches in 

 length, four inches and a quarter in circumference at the middle of the 

 shaft, and three inches and a half in breadth across the distal end : the 

 right femur, No. 1577? presents the same dimensions, but is two lines 

 narrower at the distal end. 



With respect to these small femora, if they had belonged to young 

 birds of the larger species, their nonage would unquestionably have been 

 indicated by the characters of the bones. The femur of a young Ostrich, 

 bearing the same proportion to that of the adult which No. 1577 bears 

 to No. 1569, has the whole upper surface of the proximal end and all 

 the distal articulation covered with thick cartilage, and the line of the 

 terminal epiphysis is conspicuous, although the uniting ossification has 

 commenced ; the trochanterian ridge is rounded off ; the surface of the 

 shaft of the bone is smooth ; the muscular ridges quite undeveloped. 

 In the small femora of the Dinornis, Nos. 1577 and 1578, no trace of the 

 separation of the terminal epiphyses remains ; the sculpturing of the arti- 

 cular surfaces is sharp and bold ; every ridge and tuberosity indicative of 

 muscular action is as strongly developed as in the largest femora. 



In comparison with the femur of the Dinornis dromioides, No. 1575, 

 the present bone, No. 1578, which is one inch and five lines shorter, has 



