_Relations._--Outer surface with the gluteus medius (Fig. 90, _b_) and the gluteus maximus. Inner surface with the gemellus superior (Fig. 163, 6), the great sciatic nerve (Fig. 163, _a_), and the flexor caudæ longus (Fig. 68, _x_). _Action._--Abductor of the thigh. =M. gemellus superior= (Fig. 163, 6).--The gemellus superior is a triangular muscle lying beneath the pyriformis (Fig. 163, 7). It is broader than the pyriformis, so that it projects beyond its borders both caudad and craniad. It is closely united craniad with the gluteus minimus, so that the limits of the two are definable only with difficulty. Its caudal border is closely united to the gemellus inferior. _Origin_ by fleshy fibres from an elongated area on the dorsal border of the ilium and ischium. The area is narrowed craniad. It does not quite reach the posterior inferior iliac spine in the one direction nor the spine of the ischium in the other direction. The fibres converge to a strong tendon the _Insertion_ of which is into a triangular area dorsad of the tip of the great trochanter. _Relations._--Outer surface with the gluteus medius (Fig. 90, _b_), the pyriformis (Fig. 163, 7), the great sciatic nerve (Fig. 163, _a_), and the gluteus maximus. Inner surface with the ilium, ischium, the capsularis, the caudal edge of the gluteus minimus (Fig. 163, 5), and the cranial edge of the obturator internus (Fig. 90, _e_). _Action._--Rotates the femur and abducts it so as to carry the foot outward. =M. gluteus minimus= (Fig. 163, 5).--The gluteus minimus is a long triangular muscle beneath the middle of the gluteus medius (Fig. 90, _b_) and with its caudal border against or covering the cranial border of the gemellus superior (Fig. 163, 6), to which it is frequently closely united. _Origin_ from the ventral half of the ilium, from near its cranial end to a point midway between the posterior iliac spine and the spine of the ischium. The muscle ends in a strong flat tendon. _Insertion_ into an oval facet at the base of the dorsal surface of the great trochanter on its lateral side. _Relations._--Outer surface with the gluteus medius (Fig. 90, _b_) and at the caudal border with the gemellus superior (Fig. 163, 6). Inner surface with the capsularis and rectus femoris (Fig. 92, _b_). _Action._--Rotates the femur so as to carry the foot out. =M. capsularis= (gluteus quartus, or epimeralis).--The capsularis is a small flat bundle of muscle-fibres which lies obliquely beneath the gluteus minimus (Fig. 163, 5) and gemellus superior (6) on the lateral or outer surface of the ilium. _Origin_ by fleshy fibres from the surface of the ilium over a triangular area between the origin of the rectus femoris (Fig. 92, _b_) ventrad, the gemellus superior (Fig. 163, 6) dorsad, and of the gluteus minimus (Fig. 163, 5) craniad and the acetabulum caudad. The muscle passes over the smooth surface of the ilium and the pubis ventrad of the acetabulum and then over the capsule of the joint.