368 PEOFESSOE OWEN ON THE GENUS DINOENIS. 



divisions diverging to the upper end of the condylar risings (ib. u, y), but subsiding 

 before attaining these. 



At the lower part of the pretrochanterian surface, midway between the head and the 

 ectotrochanterian tuberosity, is the rough surface, partly prominent, partly depressed 

 (PI. LX. fig. 1, s), which seems to represent the small trochanter in Mammals. 



The rotular cavity or channel (ib. fig. 1, t), 2 inches across and 1^ inch ui depth, 

 shows no trace of the rising marked in that part of the femur oi Dinornis giganteiis^. 

 The anterior intercondylar ridge dividing the rotular fossa {t) from the intercondylar 

 one (PI. LXI. fig. 1, v, v') is sharp. The intercondylar fossa is partially divided into two 

 depressions, the inner one (ib. v) being the deepest, the outer one (o') the largest. 

 These are divided from the popliteal cavity (PL LXI. fig. 1, 2;) by the post-intercondylar 

 ridge (ib. w), which is well marked, but shorter, thicker, and move rounded than the 

 anterior one (PL LX. fig. 2, t'). 



The entocondylar ai'ticular surface (ib. u') has the usual relative size and shape'. 



The ectocondylar surface for the tibia (ib. x) is comparatively small, measuring 

 1 inch 9 lines by 1 inch in extent ; it is continued over the ridge-like posterior pro- 

 jection of this part of the condjde to that on the concavity or groove for the head of 

 the fibula (PL LXI. fig, 1, y), which groove is feebly divided into an upper (y) and 

 lower {y") tract. 



The popliteal space (Pl. LXI. fig. I , z) has the usual dinormthic depth, shape, size, 

 aRd oblique direction. It is rugous ; and some small foramina at its deepest part are 

 the sole representatives of a pneumatic system, though probably related only to the 

 transmission of vessels. 



The contrast is striking, in placing by the side of the above-described bone the femur 

 pf any of the species of large existing Struthious birds, in regard to every indication of 

 the strength and vigour of application of the hind limbs. The chief results of the 

 comparison of the femm- of Ditiornis with that of Struthio were recorded in the original 

 Memoir on the first received bones from New Zealand^ But the femur of the Emu 

 (Dromaius), though still smaller than that of the Ostrich in comparison with the 

 gigantic species of Binornis, is less difierent in shape. The shaft of the bone is 

 rounder than in the Ostrich ; but the antero-posterior diameter of that part is less 

 than in Dinorm's. There is no trace of the bifurcate ridge on the fore part of the 

 shaft, and very feeble indications of " linese asperse " on the back part ; of the tube- 

 rosities there developed in Binornis no rudiment even is present in existing Stru- 

 thionidse. The meduUarterial canal is very minute in Bromaius, as in other pneumatic 

 femora; and the associated large air-hole at the back part of the upper end of the 

 femur significantly differentiates Dromaius, as it does the other large existing Stru- 

 thionidse, from Binornis. The head is sessile ; one cannot predicate a cervix in the 



' Trans. Zool. Soc. yol. iii. pl. 44. fig. 2, r. 



' lb, ib. pl. 46. fig. 3, t {Binornis casuarinus). ' lb. ib, (1843) p, 249. 



