624 Mk, P, CHALMERS MITCHELL ON THE [June 16, 
which is separate and muscular in Palamedea, separate and 
tendinous in Gallus. 
Temporalis.—The superficial portion of this muscle is very large 
and inseparable into layers ; it arises from the whole temporal fossa, 
and from the external and internal surfaces of the mid-temporal 
process ; it runs forwards and downwards under the quadrato- 
maxillary bar to the outer upper surface of the lower jaw; internal 
to this, and arising from the deeper region of the temporal fossa, 
is a strongly marked pyramidal muscle, which ends in a stout 
tendon inserted to the inner surface of the lower jaw. A still 
deeper portion runs across from the forward process of tlie 
quadrate to the inner side of the ramus. Lastly, a wide band of 
muscle bridges the narrow interval between the inner edge of the 
forward process of the quadrate and the wall of the orbit behind 
the optic foramen. 
Pterygoid.—A superficial portion, similar to that found in Ducks 
and Geese runs from the ventral, posterior end of the lower jaw to 
the palatal membrane. It is not so tendinous as in the Ducks and 
Geese. The deeper portion of the pterygoid is an almost continu- 
ous mass of muscle, inseparable into regions, from the pterygo- 
palatine area to the lower jaw. 
MUscies oF THE LEG. 
Variations in the Conditions of the Ambiens. 
In the musculature of the leg there are several points (illus- 
trated by figure 3, p. 625, and figure 4, p. 626) to which I wish 
to refer. As Garrod showed, the four muscles which he called 
A, B, X, and Y, the femoro-caudal and its accessory, the semiten- 
dinosus and its accessory, are all present. The interconnections 
between the muscles at the back of the knee differ so in birds that a 
description of their exact condition in Opisthocomus may be placed 
on record, although I have not yet sufficient material to make 
comparisons of any value. 
The adductors have no insertion to the tibia, but send a strong 
slip to the middle head of the gastrocnemius. The semimem- 
branosus, the most posterior of the thigh-muscles, runs straight in 
to the tibia, unconnected with the tendon of the semitendinosus. 
The accessory semitendinosus is very broad and strong, but does 
not nearly reach the tibia, being separated from that by the middle 
head of the gastrocnemius. The semitendinosus, after being 
joined by its accessory, sends in one fibrous slip to the tibia, 
proximal to that of the semimembranosus; while the greater mass 
of the muscle ends in a strong tendon, which runs down alongside 
and soon fuses with the middle head of the gastrocnemius, before 
that reaches the tibial head. 
The condition of the ambiens muscle is still more interesting. 
Garrod (see paper referred to above) examined the legs of three 
specimens of Opisthocomus. In all cases he found the ambiens 
small, but normal, above the thigh. In five of the six legs it was 
