No. 406.] DINOSA UR-AVIAN STEM. 785 
shown in Fig. 3 there are 
two muscles at the back 
of the femur, the larger of 
which, or *ischio-femoral," 
passes from the crest of 
the fourth trochanter back 
to the ischium ; while the 
more slender caudo- 
femoral ” passes from the 
apex of the fourth trochan- 
ter back to the caudals and 
causes the sudden lateral 
movements of the tail, so 
characteristic of the duck. 
The pronounced develop- 
ment of this character in 
Iguanodon indicates a 
very powerful ‘caudo- 
femoral" muscle in this 
type. Further, Dollo ob- 
serves that Hesperornis, 
with its well- developed 
tail, presents a condition 
of the fourth trochanter 
intermediate between the 
avian and dinosaurian 
types. 
Returning to the car- 
nivorous bipedal dinosaurs, 
Osborn (99 (2) p. 163) 
described the complete 
hand and foot of Mega- 
losaurus from the famous 
Bone Cabin Quarry. Of 
greatest interest is the 
first digit, or hallux, not 
RXVTNMERUITMQU META a TA E 
e 
), right hind 
Fic. 4.— Carni li (All 
limb, x 3s. After Osborn. 
before described; proximally the metatarsal of this toe (I) 
persists and fits into a shallow groove of metatarsal II ; the 
