20 
sisting of two distinct portions—a posterior costal from the first three 
ribs, and an anterior part from the six lowest cervical vertebrz. The 
fibres of the former converge to the inferior angle of the scapula, and 
those of the latter to the vertebral margin. In addition he describes* 
two levatores anguli scapulae, one or both of which, however, are more 
probably to be looked upon as of the nature of “ acromio-trachelien ” 
muscles. 
In Chlamydophorust the serratus magnus is large, single and un- 
divided, the levator anguli scapulae being unsegmented from it. In 
Tatusia and Dasypus, Macalister{ found it bipartite, the anterior costo- 
cervical part including levator anguli. 
Humphry§ recognises in the Ai both anterior and posterior serratus 
factors and levator anguli, and Macalister|| found the same in Cyclo- 
thurus. - 
In Orycteropus and several other Edentates? the “ trachelo-costo- 
scapular’ system of fibres is either continuous or imperfectly divided. 
In Agouti and various other Rodents** (Guinea Pig, Rabbit, and 
Hare) conditions obtain similar to those just described, i.e., there is a 
*trachelo costo scapular” muscle corresponding to the serratus magnus 
and levator scapulz. In Agouti it is indivisible; in the other forms 
there is a line of separation in the muscular sheet opposite the third 
rib, which Mivart and Murie regard as marking off the levator. Inthe 
Rabbit Leche++ follows Krause in regarding as the true levator anguli 
a distinct muscle which others{{ regard as a rhomboideus capitis. 
In Talpa$$ the serratus and levator scapulz are distinct, and the 
former purely costal in origin. So alsoin Hrinaceus and Chrysochloris|||\, 
though in the latter the anterior border of serratus is overlapped by 
the levator. In Gymnura, however, according to Dobson, the serratus 
magnus is “very large, consisting of a cervical and a thoracic portion, 
the former the united levator anguli scapule.” 
In most Carnivora the trachelo-costo-scapular muscle is a continuous 
sheet. 
M. subclavius (fig. 3, s, and figs. 6 and 7, s.c.) takes origin 
from the anterior border and part of the ventral surface of the 
first costal arch, being attached to, and around, the prominent 
tubercle on the anterior border of the rib. At this point the 
costal arch exhibits in some specimens a segmentation into ver- 
tebral and sternal portions, in the shape of a synchondrosis whose 
plane cuts the tubercle obliquely. The muscle thus arises from 
adjacent portions of doth sternal and vertebral rib-segments. 
This subdivision is not visible in all specimens. 
The muscle thus arising is comparatively narrow at its origin, 
but spreads out into a broad and slightly tendinous band as it 
proceeds forwards and outwards to its insertion, which is into 
the mesial border of the ‘‘ mesoscapular segment ” of the shoulder- 
girdle, partly into the adjacent part of the mesial border of the 
* XXxVilil., page 478. txxvil., page 242. txxvii., page 242. §xxii., 
page 32. || xxvil., 242. ‘I xv., page 570, and xxvii., page 243. **xl., page 
393. ttxxvi., page 730. {tlvi. and xl., page 393. §§xi., page 212. 
|| xxvi., page 767. I vili., page 394. 
