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



Qmnlrirrjis I'.rtrtisnr. — Iii both Thylacine and Cuscus the rectus femoris (PI. III. 

 fig. 1, r.f., and PI. IV. fig. 5, r.f.) has a double origin. In the latter, the reflected head is 

 much the larger of the two ; the other head, although quite distinct, is a very slender 

 tendon indeed. In the TJiylacine, the reflected head is also strongly marked (PL IV. 

 fig. 2, r.f 2 .), but the other head is developed to an enormous extent, and strongly reminds 

 one of the appearance presented by the long head of the triceps in the fore limb of the same 

 animal (PI. I. fig. 5, t.r 1 .). It takes origin by a thin aponeurosis which is attached to the 

 entire length of the lower border of the ilium from the reflected tendon behind to the 

 anterior superior spine of the ilium in front. This aponeurosis gives place to a thick 

 fleshy triangular portion of muscle, which joins the belly of the reflected head to form 

 the mass of the rectus femoris. 



Young 1 describes the rectus femoris as possessing two heads in the Koala, and 

 Professor Owen 2 mentions a similar condition of the muscle in Perameles lagotis. 

 Macalister, 3 however, states that in Phalangista vulpina, the Opossum, the Wombat, the 

 Tasmanian Devil, the Giant Kangaroo and Bennett's Kangaroo the rectus femoris arises 

 by a single head from the anterior inferior spine of the ilium. 



Of the other factors of the quadriceps the vastus externus is the most strongly 

 developed. It alone also is partially separable from the others. The vastus internus and 

 the crureus are intimately blended, the one with the other. In the discus there was a 

 very distinct subcrureus ; in the Thylacine, however, there was no trace of such a muscle. 



In neither animal is there an osseous patella, but the different portions of the 

 quadriceps, together with the sartorius, unite to form an exceedingly dense and thick 

 tendinous expansion in front of the knee-joint. This is so excessively tough and 

 resistent to the knife that it almost resembles fibro-cartilage in its consistence. In the 

 AVombat 3 it apparently attains a cartilaginous structure. 



Psoas and Iliacus. — In the great majority of the Marsupial group the psoas parvus 

 attains a greater size than the psoas magnus. In the two animals under consideration it 

 is much the larger, and takes origin from the bodies of six vertebras (viz., the last dorsal 

 and the anterior five lumbar). It ends in a long round tendon, which is inserted into 

 the anterior border of the pubic bone, close to the os marsupium, and immediately in 

 front of the acetabulum. 



In the Cuscus the psoas magnus arises from the bodies of the last two lumbar 

 vertebras, and also from the upper part of the sacrum. It blends with the iliacus. 



In the Thylacine the psoas magnus consists of two distinct portions. The anterior 

 part is the larger of the two; in front it is blended with the psoas parvus, whilst behind 

 it springs from the bodies, and transverse processes of the last two lumbar vertebras. It 

 ends by joining the iliacus. The posterior portion springs from the last lumbar vertebra, 



1 Muscular Anatomy of the Koala, Jour. Anat. and Phys., vol. xvi. - Todd's Cyclop., vol. iii. p. 290. 



3 Muscular Anatomy of Tasmanian Devil and Wombat, Ann. and Mag. Nat. Hist., vol. v., 4th ser. 



