351 
end. The intercnemial surface (ib. fig. 1, £), slightly concave across at its upper part, 
becomes almost flat below. The ectocnemial surface (ib. fig. 2,7) is uniformly and 
more deeply concave across; it is 14 inch in width. 
There are (pneumatic ?) foramina (ib. fig. 2, 7,7) behind and below the intercondylar 
surface. 
A low longitudinal ridge bounds internally the posterior flat tract of the upper half 
of the shaft, and opposite the fibular ridge inclines forward and to the inner side of the 
shaft. The medullarterial orifice (ib. fig. 2, 2) is on the inner side of the fibular ridge, 
one inch above its end. 
As the shaft descends the flatness of its back part gradually becomes convex across, 
and loses the rough reticulate shallow markings indicative of muscular origin. The 
ridge (g') continued from the procnemial process, longitudinally and pretty equally 
bisects a great part of the anterior surface of the shaft, and gives the three-sided 
character to that part of the bone. On the inner and anterior part of the tibia, 
3 inches from the proximal end, is a rough low ridge and surface (ib. fig. 1, 0), an- 
swering to the stronger prominence in the Cnemiornis (marked g in fig. 1, Pl. LX1X.,). 
The extensor canal (Pl. XLII. fig. 1, »), its bridge (qg), and lower outlet (7) repeat or 
retain the dinornithic characters'. The tuberosity from the outer pier of the bridge 
is strongly developed. A flat, rough surface, 34 inches in extent, pointed above and 
broadening to 10 lines below, marks the inner side of the distal end of the shaft. On 
the other side of that part is a rough, narrow surface, suggesting a third attachment of 
the pointed end of a long and slender fibula. ‘The configuration of the distal trochlear 
articulation closely adheres to the dinornithic pattern. The shallow pit receiving the 
ectocondylar convexity is well defined. 
The epicnemial process is developed as an epiphysis; it retains this character in the 
tibia, 14 inches in length, of a young Emu (Dromaius nove-hollandie), and includes the 
commencement of the procnemial and ectocnemial ridges; it might pass for a distinct 
bone (the patella), as the distal epiphysis (ib. fig. 4, @, v) has been conjectured to 
represent an astragalus; but the cartilaginous homologue of the patella in Dromaius, 
which plays upon the rotular groove of the femur, is ossified in some birds, notably in 
the Penguins and Loons (Colymbus), in which the development of the epicnemial process 
is in excess’, and with which the true patella coexists. 
The distal epiphysis (Pl. XLII. fig. 4) has effected a closer union with the shaft of this 
tibia, agreeably with the law of its relation to the course or direction of the medullary 
artery ; the portion of the shaft developed epiphysially (ib. @) with the trochlear articu- 
lations (4) ascends nearly three inches up the fore part of the diaphysis, and develops 
the groove and process for the ligamentous bridge of the “ tibialis anticus” tendon. 
1 These are shown, in contrast with those in the tibia of Gastornis parisiensis, in the ‘ Quarterly Journal of 
the Geological Society,’ 1856, pl. iii. figs. 1 & 2, p. 204. 
? Owen, ‘ Anatomy of Vertebrates,’ vol. ii. p, 83. fig, 34, 1. 
