478 DR. R. W. SHUFELDT ON [Nov. 16, 
muscle being thin and closely pressed to the pelvis. The fibres 
converge as they near the femur and terminate in a strong, flat 
tendon which becomes inserted on the outer aspect of the trochanter 
of that bone, which insertion is slightly overlapped by the tendon 
of the gluteus medius muscle. 
The adductors arise from the infero-external margin of the 
ischium, between the anterior edge of the semimembranosus and the 
obturator foramen. 
The adductor longus (Plate XLV. fig. 1, a./) is the more anterior 
of the two and consequently arises the higher on the pelvis, and 
comes off in front of the adductor magnus, which it largely overlaps. 
Its fibres pass obliquely to the posterior aspect of the shaft of the 
femur, down which they become inserted as far as its middle, along 
the linea aspera, a line which is well marked in our subject. 
The adductor magnus (Plate XLV. fig. 1, a.m), like the one just 
described, is also a broad ribbon-like muscle, arising from the ischium 
between the semimembranosus and a middle point on the underside of 
the adductor longus, close up to its semitendinous origin. Anteriorly 
its margin is free, while posteriorly it is juxtaposed to the anterior 
border of the semimembranosus. Passing parallel with those of the 
other adductor, its fibres are inserted into the distal moiety of the 
linea aspera of the femoral shaft, down to the intercondyloid notch 
of that bone, where this muscle makes a very substantial insertion. 
Removing all the muscles of the thigh thus far described, we find 
that in this region we have the following ones remaining. They are 
shown in my drawing (Plate XLV. fig. 2), together with a few as 
yet undescribed muscles of the leg. 
A very important muscle is the obturator internus (Plate XLY. 
fig. 2, 0.2), and in Geococcyx it exists as we find it in the majority 
of the class. Prof. Garrod laid some stress on the point whether 
this muscle arose from a triangular or an oval area. Here it arises 
from a decidedly oval one, and as usual this is from the mesial sur- 
faces of the ischium and the post-pubic element of the pelvis. Its 
tendon emerges from the obturator foramen, and overlapping the 
gemellus muscle, passes to the outer aspect of the upper part of the 
trochanter of the femur, where it is inserted. 
The gemellus (Plate XLV. fig. 2, ge) is a short, thick, carneous 
muscle, which arises about the outer rim of the obturator foramen of 
the pelvis. Its fibres passing obliquely upwards and forwards are in- 
serted with the tendon of the obturator internus muscle on the tro- 
chanter of the femur. This bird also has a few of the fibres of its 
gemellus muscle inserted into the tendon of the obturator externus 
muscle, at least I found this to be the case in the specimen before me. 
We find the vastus internus (Plate XLV. fig. 2, v.i) to be a strong, 
fusiform muscle, that is only fully discovered after we have removed 
the ambiens and the adductors. It lies on the postero-internal aspect 
of the shaft of the femur, arising from the linea aspera nearly as high 
up as the head of that bone, and increasing in bulk as it descends, 
still making attachment to the linea aspera, it only becomes free 
just above the condyles. At this point it terminates in a flat tendon, 
which, crossing the articulation of the knee, becomes inserted into the 
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