MUSCULAR SYSTEM OF THE RED HOWLING MONKEY 149 



resemblance to those of the howling monkey. There is in all of them a 

 division of the pectineus into two portions which are suppUed by the 

 femoral and the obturator nerve, respectively, and the separation of 

 the adductors is not very clear (Hill, 1962). According to Bodini 

 (1965), the pectineus is not divided in Ateles, and her observations of 

 the adductors in this genus reveal these muscles as almost impossible 

 to individuahze. The resemblances of these animals to the howler in 

 reference to this group of muscles apply also to Cebus. Bodini (1965), 

 however, did not find an adductor brevis in the two specimens of 

 capuchin she studied. 



POSTPELVIC 



The observations of other authors (Bodini, 1965; Hill, 1962; 

 Sirena, 1871; Waterman, 1929) on the ventral postpelvic muscles 

 of Alouatta do not call for any special comments. 



M. obturatorius internus: Forming the outer wall of the ischiorectal 

 fossa, its origin is from (1) the inner surface of the upper arm of the 

 pubis up to the ihopubic junction, (2) the body of the pubis, (3) the 

 ischiopubic bar, and (4) the obturator membrane. Its fibers converge 

 toward the upper ramus of, the ischium where they form a tendon 

 which sometimes is divided into two. This passes over the rudimentary 

 lesser sciatic notch and into the deep part of the gluteal region. After 

 crossing behind the neck of the femur, the tendon ends on the tro- 

 chanteric fossa (figs. 40, 41). 



Nerve supply: The pudendal nerve sends a branch to the muscle 

 in the pudendal canal. 



M. gemellus superior: This is a small and somewhat rectangular 

 belly composed of thick fleshy bundles arising from the femoral side 

 of the sciatic spine and the upper part of the lesser sciatic notch 

 (fig. 36). It crosses over the iliofemoral articular capsule to end 

 at the bottom of the trochanteric fossa together with the tendinous 

 fibers of the internal obturator and the other gemellus (fig. 40). 

 The tendon of the extrapelvic portion of that muscle is applied against 

 the posterior border of the gemellus, which is here grooved to lodge 

 that tendon. The muscle is perforated by its nerve which continues 

 distally deep to the internal obturator to supply the other gemellus 

 and the quadratus femoris. 



Nerve supply: The nerve to the two gemelli and the quadratus 

 femoris (fig. 35). 



M. gemellus inferior: It is of similar shape as its homonym and 

 of approximately equal size. The gemellus inferior is found between 

 the extrapelvic portion of the obturator internus and the upper 

 border of the quadratus femoris. It arises by fleshy fibers from the 

 femoral surface of the body of the ischium near the tuberosity and 

 adjacent border of the lesser sciatic notch (figs. 36, 41). These fibers 



