32 THE VOYAGE OF H.M.S. CHALLENGER. 



Myology of the Hind Limb. 



I regret that in this chapter I am only able to give an account of the myology of the 

 hind limb in the Thylacine and Cuscus. The pelvis and posterior limbs of the Phas- 

 cogale were so shattered with shot that it was impossible to conduct a proper examina- 

 tion of their anatomy. 



Gluteal Region. 



Gluteus maximus (ecto-gluteus) (PI. III. fig. 1, ec.g 1 ., ec.g 2 ., ec.g 3 . ; and PL IV. fig. 5, 

 ec.g 1 . and ec.g 2 .). — In the Cuscus the gluteus maximus is represented by three muscles all 

 occupying the same plane, and placed superficial to the other structures of the gluteal 

 region. These three muscles arise in a continuous line from the anterior superior spine 

 of the ilium in front to the fourth caudal vertebra behind. The two posterior muscles 

 are only partially separated from each other, and they together represent the agitator 

 caudae. The anterior muscle is the combined gluteus maximus and tensor fasciae femoris. 



The agitator caudae (PI. III. fig. 1, ec.g 2 ., ec.g 3 .) is a large, powerful muscle. Its 

 anterior and smaller portion arises from the fascia over the hinder part of the sacrum 

 and from the first caudal vertebra ; the wider posterior portion springs from the fascia 

 over the second caudal vertebra and from the transverse processes of the third, fourth, 

 and fifth caudal vertebrae. Both portions of the muscle are inserted into the posterior 

 aspect of the femur in a continuous line from the root of the great trochanter above to 

 within an inch of the external condyle below (ec.g 2 . x and ec.g 3 . x ). 



The combined gluteus maximus and tensor fasciae femoris (PI. III. fig. 1, ec.g 1 .) is a 

 thin layer of muscular fibres which arises from the fascia over the last lumbar vertebra 

 and the sacrum, from the fascia over the gluteus medius (meso-gluteus) muscle and 

 also from a tendinous cord which passes horizontally backwards from the anterior 

 superior spine of the ilium. This fibrous cord is fully an inch and a half long, and 

 gives origin by its superior border to the three gluteal muscles, whilst by its inferior 

 margin it gives attachment to the sartorius and the obliquus internus. At first sight 

 it has the appearance of being the representative of Poupart's ligament, but it cannot in 

 any respect be considered the homologue of this structure, seeing that the aponeurosis of 

 the external oblique is in no way connected with it. The gluteus maximus is inserted 

 into the outer aspect of the root of the great trochanter, and also slightly into the 

 posterior aspect of the shaft of the bone below this. The posterior margin of the muscle 

 is free, and quite distinct from the agitator caudae ; in front, however, it winds round the 

 anterior border of the meso-gluteus (PI. III. fig. 1, ec.g 1 . x ), and becomes inseparably 

 connected with the gluteus minimus (endo-gluteus). In this manner, therefore, the 

 superficial and deep gluteal muscles enclose the meso-gluteus on all sides except 

 posteriorly. That the anterior fibres of the muscle just described represent the tensor 



