874 DR. 0. F. SONNXAG ON THE MYOLOGY 



the lumbar vertebrae. The psoas parvus exceeds the magnvis irl 

 all forms, but the disproportion is not so great, and the parvus is 

 more tendinous in Phascolomys. Macalister (18) describes it as a 

 weak muscle in the latter. It is inserted into the pubis behind 

 the corresponding marsupial bone in all forms. 



Muscles of the Anterior Extremity. 



The Dorso-epitrochlearis arises from the posterior border of the 

 latissimus dorsi and its tendon in Phalanger and Fseicdochirus, 

 a,nd it remains muscular to its insertion into the tip and inner 

 border of the olecranon. In Phascolarctos it is thin, and a 

 considerable part is fascial. In Phascolomys it arises chiefly from 

 the tendon of the latissimus, and it is firmly bound down by deep 

 fascia. When the fore-limb is abducted the muscle becomes tight 

 soonest in the latter. And the distant extremity is more 

 evidently continuous with the anconeus internus in Phascolarctos. 



Pectoral Muscles : — Cunningham (2 ) analysed the pectoral mass, 

 and desci'ibed a pectoralis major composed of superficial and deep 

 parts, a pectoralis minor, and a pectoralis quartus. In my 

 specimens tlie conditions present differed in some respects from 

 those described by Young, Cunningham, Macalister, and others. 



Pectoralis Major :— In Phascolomys Macalister (18) showed that 

 the superficial part has clavicular, sternal, and costal origins. In 

 my specimen (text-fig. 39 A) it arises from the mid-sternal line 

 and fascia over the abdominal muscles in the infra-sternal fossa; 

 there is no clavicular nor costal origin. It is inserted into the 

 pectoral crest of the humerus and fuses extensively with the 

 clavicular deltoid. The deep part arises from the manubrium 

 sterni, crosses the pectoralis minor and quartus, and is inserted 

 by a narrow tendon into the outer tuberosity and upper part of 

 the pectoral crest. It is separated from the first part. In 

 Phalanger the superficial part does not arise from the entire 

 length of the sternum, but in other respects it resembles the 

 superficial part in Phascolomys. The deep part has a more 

 extensive origin from the body of the sternum. In Pseiidochirns 

 the conditions ai-e similar to those in Phalanger, but it is difficult 

 to distinguish the superficial part from the clavicular deltoid in the 

 fused muscular mass. In Phascolarctos the superficial part has an 

 origin from the inner third of the clavicle, so the clavicular deltoid 

 does not reach the sterno-clavicular joint as it does in Phascolo7nys. 

 I have already described and figured muscles resembling those in 

 the latter in Mandrillus leucophceus. 



Pectoralis Minor: — In Phascolomys it arises from the posterior 

 three-fourths of the sternum, and it is inserted into the great 

 tuberosity, coraco-liumeral ligament, and coracoid process. It 

 remains separate from the quartus, but their insertions are 

 contiguous. In Pseudochirus the minor and quartus are in 

 contact throughout the greater part of their course. But in 

 Phalanger and Phascolarctos they are separate. 



Suhclavius : — The insertion varies. In Phalanger it is attached 



