REPORT ON THE MARSUPIALIA. 3 



the head of the humerus, so as to clothe the humerus on its anterior and outer aspects, 

 and is inserted differently in each animal. In the discus a very few of these anterior 

 fibres — those constituting the anterior free margin of the muscle — are attached to the 

 clavicle. The remainder are continued downwards, and fuse with the acromial and clavi- 

 cular portions of the deltoid. In the Phascogale the insertion of this part of the trapezius 

 is precisely similar, with the exception that none of the fibres join the acromial deltoid — 

 all enter the clavicular portion of that muscle. In the Thylacine the humeral division of 

 the trapezius is more strongly marked than in either of the two preceding animals. In pass- 

 ing over the rudimentary clavicle, some of its deeper fibres mix with those of the other 

 muscles attached to this bone, and it ends entirely in the clavicular deltoid (PL I. fig. 4, tr.). 



According to Professor Macalister the humeral division of the trapezius in the 

 Wombat is in no way attached to the clavicle, but, gliding over it, replaces the clavi- 

 cular deltoid ; in the Tasmanian Devil, on the other hand, no portion of the muscle 

 reaches the humerus — all its fibres being inserted into the scapular spine, acromion 

 process, and the outer fourth of the clavicle. 1 In the Perameles the anterior fibres of 

 the trapezius are described by Professor Owen 2 as " being directly continued into the 

 pectoralis major." Whilst the scapular or posterior portion of the trapezius therefore 

 appears to be very constant in its insertion, the anterior or humeral part is subject to 

 considerable variations. 



Rhomboideus. — In none is this muscle divisible into its three constituent parts. In 

 each of the three specimens it forms a continuous muscular layer, which arises for a vary- 

 ing extent from the occipital crest under cover of the trapezius and the eleido-occipital 

 when this muscle exists, from all the cervical and from the two anterior dorsal spines. 

 In the duscus and Phascogale the occipital origin is relatively wider than in the 

 Thylacine. Those fibres which spring from the dorsal, and from the two or three cervical 

 spines, are disposed in much coarser fasciculi than the fibres in the anterior part of the 

 muscle, and they probably represent the rhomboideus proper. The entire muscle is 

 inserted into the whole extent of the base of the scapula. 



In the Phascogale the lower margin of the muscle, as it approaches the scapula, fuses 

 with the upper border of the acromio-trachelien muscle, and in this manner it is inserted 

 to a small extent into the root of the scapular spine. 



Macalister l describes a more extensive origin of the rhomboideus in the Wombat. In 

 this animal it extends back as far as the fourth or fifth dorsal spine. In the Tasmanian Devil, 

 according to the same authority, it consists of two distinct portions, viz., a rhomboideus 

 occipitalis and a rhomboideus proper composed of the amalgamated major and minor. 



Acromio-trachelien (the omo-atlantic of Haughton and Macalister). — In the discus 

 and Phascogale this muscle is double ; in the Thylacine it is single. 



1 Myology of the Wombat and Tasmanian Devil, Annals and Magazine of Natural History, vol. v. 

 * Comparative Anatomy and Physiology of Vertebrates. 



