Prof. Owen on Bones of Dinornis and Palapteryx. 463 



spending ridge formed by the meeting of the vasti-muscles along the 

 fore part of the shaft is shorter in Bin, gracilis than in Bin. stru- 

 thioides. 



The most marked distinction, however, is presented by the distal 

 extremity of the bone, which is not only relatively less expanded in 

 the Bin. gracilis^ but the rotular groove is narrower, and is bounded 

 laterally by condyloid eminences of more nearly equal length ; the 

 external one not rising so high up, nor describing the sigmoid curve 

 in descending, as in the Bin. struthioides. The rotular groove in the 

 Bin. gracilis is impressed by a transversely oval rough depression, 

 at its upper part, with sharp lateral borders ; which depression does 

 not appear in any of the femora of the Bin. struthioides. The 

 popliteal space is triangular and better defined in the Bin. gracilis ; 

 the fibular groove is shorter and less angular, and the rough deep pit 

 above it is smaller. The tibial surface on the inner condyle is rela- 

 tively smaller. 



Tibia. 



The same character is repeated on the proximal end of this bone, 

 where the surface applied to the inner condyle is absolutely smaller 

 than in the Bin. struthioides, although the entire bone, as shown in 

 the subjoined admeasurements, is longer in the Bin. gracilis : it is 

 also, as the name of the species implies, more slender in proportion 

 to its length. 



D. gracilis. 

 in. lin. 



The entire length of the bone is 23 6 



The transverse breadth of its proximal end .... 5 2 



The transverse breadth of its distal end 2 10 



The circumference of the middle of the shaft . . 4 6 

 The fibular ridge extends down the shaft .... 9 6 



But this ridge commences nearly 3 inches below the back part of 

 the proximal end of the bone, nearer the outer side than in the 

 B. struthioides : it is interrupted by an oblique smooth tract at the 

 point indicated in the admeasurement, where the medullary artery 

 penetrates the bone ; it then reappears about one inch and a half be- 

 low the interruption, and soon gradually subsides. This second lower 

 part of a fibular ridge is better marked than in the Bin. struthioides. 

 The relative size and position of the procnemial and ectocnemial 

 ridges are much the same as in the tibia of the Bin. struthioides and 

 Bin. dromioides. 



Metatarsus. 



The difference between the Bin. struthioides and the Bin. gracilis 

 is more obvious at first glance in a comparison of their metatarsi than 

 in that of the above-described bones ; especially to an eye accustomed 

 to the comparison of the metatarsi of the different species. The 

 superior length and slenderness of that bone in the Bin. gracilis 

 would at once prevent its being confounded with the metatarsus of the 

 Bin. struthioides. 



