34 
inner condyle is not sharp ; the rotular groove (ib. fig. 1,^) is deep and moderately wide, 
with the inner boundary, formed by the narrow anterior part of the inner condyle (ib. 
fig. 6, e'), most produced. The breadth of this end of the longer femora is 1 inch 9 lines ; 
the character of the distal articular surface is shown in PI. IX. fig. 5. 
The head, neck, and great trochanter (PI. XL fig. 6) are occupied by a pneumatic 
cancellous structure, with a thin compact wall on the upper part and sides : this begins 
to gain thickness at the under part of the neck and at the lower and back part of the 
trochanter, the compact wall acquiring a thickness of a line at the beginning of the 
shaft, where the cancellous structure is confined to the outer side of the pneumatic 
cavity ; this structure gives way to a few delicate filaments of bone crossing the cavity 
of the major part of the shaft, and is not resumed until the bone expands to form the 
distal condyles (ib. fig. 7). 
The five tibiae of Bidus in the same collection range in length from 8 inches 8 lines 
to 9 inches. The procnemial ridge (PL X. figs. 1, 2, 4, ])) is a triangular plate, with 
the base longest and the apex rounded off ; it inclines outwardly, and does not extend 
much more than half an inch from the level of the proximal end of the bone : the 
length of its base rather exceeds an inch : on its inner side a triangular muscular sur- 
face is well defined by an irregular inferior line or ridge (ib. fig. 2, n). The ectocnemial 
process (ib. figs. 1, 3, 4, e) is thicker, shorter, and terminates roughly and obtusely. 
There is a low, narrow ridge (ib. fig. 2, g), about half an inch in length, on the inner 
side of the proximal end of the shaft, beginning about 9 lines below the articular sur- 
face at that end. The fibular ridge (ib. figs. 1 & 3, h), beginning 1 inch 8 lines from 
the proximal end, extends about 2 inches down the outer side of the shaft. The epi- 
cnemial ridge (ib. figs. 1 & 4, is obtuse, and but little produced above the upper 
articular surfaces or condyles {t d) oi the tibia : the breadth of that end of the bone, 
in the longest specimen, is 2 inches 3 lines. The tendinal canal at the fore part of 
the distal end is bridged by bone (ib. fig. 1, 1), and is situated on the inner half of that 
aspect of the shaft ; the lower opening is subcircular and close to the anterior end of the 
inner lower condyle (ib. a), which is more produced forward than the outer one (ib. b). 
Their hind ends project very little beyond the level of that aspect of the shaft of the 
tibia. An intermuscular ridge (ib. fig. 1, r) strengthens into a tuberosity (/) at the inner 
side of the tendinal groove. 
The cancellous structure in the tibia is limited to an extent of about half an inch 
below the proximal articular surfaces (PL XI. fig. 8), and to about an inch and a half 
from the distal end of the line (ib. fig. 9) : the shaft is occupied by a large air-cavity, 
with a compact wall of half a line in thickness at the upper third, gradually increasing 
to about a line at the lower fourth, until the cancellous structure is reestablished ; the 
transverse direction of a plate of this structure indicates the extent of the original 
distal epiphysis of the tibia (fig. 8). 
The fibula (PL X. figs. 6-8) presents the usual ornithic characters of the bone : 
