REPORT ON THE MARSUPIALIA. 33 



fasciae femoris is shown by the fact that a twig from the superior gluteal nerve can be 

 traced into their midst (PI. III. fig. 1, s.g.n.). 



In almost all the muscles of the gluteal region of Thyladnus there is a marked 

 tendency to segmentation. The gluteus maximus (PL IV. fig. 5, ee.gr 1 . and ec.g 2 .) 

 differs materially from the corresponding muscle in discus. It consists of two portions 

 which lie one behind the other, and each is segmented into a superficial and deep part. 

 The posterior division represents the agitator caudse. The anterior part or gluteus 

 maximus proper lies altogether behind the gluteus medius (meso-gluteus). Its super- 

 ficial segment springs from the fascia on the dorsal aspect of the sacrum. It is a thin 

 fleshy stratum which is inserted into the back part of the great trochanter (ec.g 1 *.). The 

 deep segment, narrower but more fleshy than the superficial part, takes origin from the 

 side of the sacrum in its posterior half, and also from the fascia on the dorsum of the 

 sacrum ; it emerges from under cover of the superficial segment near the trochanter 

 major, and is inserted into the posterior aspect of the femur immediately below its fellow 

 (ec.g 1 *.). 



The agitator caudse (ec.g 2 .) by its superficial segment springs from the fascia over the 

 anterior three caudal vertebrae, and by its deep segment from the transverse process of 

 the second caudal vertebra. The latter is a very narrow band, and after a short inde- 

 pendent course they unite to be inserted into the posterior aspect of the femur below 

 the deep segment of the gluteus maximus (ec.g 2 *.). 



The four muscular factors which in Thylacinus thus represent the gluteus maximus 

 in man are supplied by a special nerve from the sacral plexus. In the Thylacine there is 

 apparently no trace of the tensor fasciae femoris. 



Gluteus medius (meso-gluteus). — In both animals this muscle is powerfully developed 

 and quite distinct from the gluteus minimus. In Cuscus (PL III. fig. 1, m.g.) it is a 

 thick fleshy muscle which arises from the short iliac crest, from the dorsum ilii, from the 

 fascia covering it, and from the tendinous cord already referred to as giving common 

 origin to the three gluteal muscles. It is inserted into the summit and outer aspect of 

 the great trochanter of the femur (m.g. + ). 



The gluteus medius in the Thylacine (PL IV. fig. 5, m.g.) is segmented into a super- 

 ficial and deep portion. The former is inserted into the outer aspect of the great 

 trochanter (m.g*.), whilst the latter is attached to its summit. The deep segment is not 

 so broad or fleshy as the superficial part, and is received into a deep hollow in its under 

 surface, so that at first sight it appears as if the one segment were enclosed within the 

 substance of the other. 



In the Koala a the gluteus medius is also frequently bilaminar. 



Gluteus minimus. — This muscle is quite distinct in both animals from the gluten.-, 



1 Young, Muscular Anatomy of the Koala, Jour. Anat. and Phya., vol. xvi. p. 234. 



(ZOOL. CHALL. EXP. — PART XVI. 1882.) Q 5 



