21 
acromion, and slightly in front of this into to the fascia over the 
supraspinatus muscle. Jn its course it passes under cover of the 
clavicle, and of the cleido- and deltotrapezius. At its origin it 
lies immediately mesiad of the insertion, into the ventral face of 
the first costal arch, of the M. rectus abdominis, and immediately 
dorsal to it the great vessels of the forelimb arch over the first 
rib to enter the axilla. They are, however, sunk in the deep 
concavity behind the tubercle of origin of the muscle. Under 
cover of the tendon of insertion there stretches a strong liga- 
mentous arcuate band between the coracoid and the mesoscapular 
end of the clavicle—a coraco-clavicular ligament. As the muscle 
passes under cover of the clavicle and cleido-trapezius the post- 
axial border of the subclavius is more or less adherent to the 
deep surface of these structures, and a deep lamina of the tendon 
of insertion is attached or adherent to the coraco-clavicular 
ligament. 
The origin of this muscle amongst marsupials is a very constant one. 
It arises from the first costal cartilage as in man, or from the first rib. 
In Notoryctes no fibres from any other source of origin enter the sub- 
elavius such as Rolleston has described arising from the sixth costal 
cartilage in Wombat.* 
The insertion, on the other hand, is very variable in this order. The 
fibres are wholly arrested at the clavicle as in man in Cuscus, Phas- 
cogale,t Macropus major and minor, Phalangista cavifrons,§ and Koala 
(usually).$ 
In Thylacinus|| it is attached solely to the fascia over the supra- 
spinatus muscle, constituting a variety of sterno-scapular muscle. 
In Sarcophilus? Macalister found it attached to the clavicle only in 
one case, and to clavicle and scapular spine in another, and to clavicle 
and acromion in Didelphys ;** while in Dasyuwrus viverrinus and Phal. 
vulpinat{ it is inserted into clavicle, acromion, and supra-spinatus 
fascia, and in Wombat, by means of the latter to the whole length of 
the scapular spine (Rolleston).{{ 
In Echidna and Ornithorhynchus, according to Rolleston,$§ the sub- 
clavius muscle is represented by the epicoraco-humeral muscle of 
Mivart.||||_ This arises in Echidna from the ventral surface and outer 
border of the epicoracoid, and is inserted into the radial tuberosity of 
the humerus between the pectoral and supra-spinatus insertions and 
into a ridge running distally from this. 
The muscle in Ornithorhynchus corresponding to Mivart’s epicoraco- 
humeral has beeu figured by Meckel, as already noted, under the name 
of an anterior deltoid, and by Cuvier and Laurillard*** as a middle or 
small pectoral. 
Humphry, as against Rolleston, takes the latter view of this muscle 
in Monotremes, when he says,t+{ “I conceive the pectoralis minor to 
- i, page 626. ‘iv., page G;: £viz. Ply 195, J8l and: 179. ‘Sixxu, 
page 226, and xxvili., page 130. |liv., page 6. ‘] xxix., page 158, and 
Xxx., page 130. **xxix., page 158. +t{xxxvi., page 111. {tli., Explan. 
of fig. 3 and Pl. 47. _ §§li., page 617. _|||| xxxix., page 383. ‘I Supra p. 
Soave bl, 266, fic, 2. Th xx., page 157; 
