194 FIELD COLUMBIAN MUSEUM. - 
terminating inarugoseknob. From the middle of the shaft to the distal 
end the pubes are joined in a more or less mobile hgamentary union. 
The acetabulum is formed, in its upper half, by the inferior border, 
and the greater and lesser peduncles of the ilium; in the lower half 
by the proximal ends of the pubis and ischium. In the normal quadri- 
pedal posture the thrust of the femur is received by the inferior border 
of the ilium just below the sacricostal yoke. In the bipedal posture 
the weight would be borne by the great peduncle which is supported 
by the rib of the dorso-sacral vertebra. 
The rzbs of the dorso-sacral vertebra articulate with the anterior 
surface of the greater peduncle. Similarly the ribs of the caudo-sacral 
vertebra articulate with the postero-internal surface of the lesser 
peduncle and with the mesial wall of the iliac plate. From the point 
of articulation of each of the five sacral ribs a transverse plate extends 
upward along the mesial wall of the iliac plate. These plates in the, 
left side of the Museum specimen, have become firmly conjoined with 
the sacral ribs and the diapophyses, leaving only a small foramen 
above the sacricostal bar. . 
The femur in the Museum specimen is compressed in the shaft 
antero-posteriorly, but is otherwise splendidly preserved. (Plate L1.) 
It is a stouter bone than that of any other known Opisthoccelian except- 
ing the unusually stout-limbed form designated by the species, A. 
amplus. ‘The head is rugose and rises five centimeters above the great 
trochanter. The fourth trochanter is marked by a sharp and rugose 
ridge at the postero internal angle of the shaft, slightly above the 
middle. ‘The distal end is expanded into heavy condyles, deep 
antero-posteriorly. The outer one is cleft by a deep, fibular groove. 
MEASUREMENTS. 
FEMUR: M 
Length 252.228 ies bre 2 ee 1.830 
Breadth, head and great -trochanter,__-_...-.-.....¢_1>_ gee 570 
Breadth at-middle of shaft-s-- 22. 2. 221k 310 
Breadth, ‘distal end ssuta = O22) foes ka .590 
Antero-posterior diameter of inner condyle. _-2.-°.__. 2. 2a .410 
Inferior border of fourth trochanter,to distal endJ._2 .) 3 ae 880 
Length'of fourth’ tro¢hanter---s-----_2 -.- 3 5 2 a .400 
Antero-posterior diameter of, head __.-.. :_.. ---. J. 2 
ILIUM: . 
Length over‘alil... secon) ee. 2 2225-5 ee 1.390 
Acetabulum to"superior border - 2. ~~. 52 ..--2 be 4 ee .490 
Length of great peduncle on anterior surface__+ -2-._. 2 _ oe 
Base of great peduncle to anterior margin:___.-_.2/ 22" 2) see ” 440 
Breadth from lesser peduncle to postero-superior surface____-__- ---_-- .430 
Breadth of acetabulum)-2- 32 io0 oe the Sts 
