12 
In Phascogale* the acromio-trachelien is double, and attached to whole 
length of scapular spine, the “superior ” muscle being united with the 
margin of the rhomboideus by its upper margin, so that the latter 
muscle-is inserted “‘to a small extent into the root of the scapular 
spine.” A similar fusion also occurs in Myrmecobius.t In Cuscus the 
acromio-trachelien is also double, and distinct from the single rhom- 
boideus. In Thylacine it is single and distinct. In Sarcophilust the 
rhomboideus is distinct from the acromio-trachelien, and is itself 
divided into “a rhomboideus occipitalis (7.e., capitis), and a proper 
rhomboid made up of the fused major and minor.” 
In Dasyuwrus viverrinus and in Phalangista vulpina MacCormick$ 
found the rhomboid extensive and undivided, and inserted into the 
whole length of the base of the scapula, and also that it “has a small 
slip inserted into the anterior lip of the spinal crest of the scapula 
close to the base of the bone above the acromio-trachelien superior, 
and in a line with it.”’ 
Both in Ornitherhynchus and Echidna the rhomboid*is undivided, 
thick, and strong, its origin reaching in the former from the occipital 
crest of the dorsal region. In both forms it is inserted into the 
greater part of the scapular base. Cuvier and Laurillard|| figure an 
acromio-trachelien in Ornithorhynchus which consists of two distinct 
parts, described by Meckelf’ under the name of levatores scapule. 
The dorsal part is inserted into the scapular base, the other into 
acromion and clavicle. Mivart notes the same double muscle in 
Echidna ander the name of levator-clavicule**; also Westling.t+ 
Macalister{{ states that in Dasypus the acromio-trachelien is supra- 
occipital in its origin, that in Pholidotus it is united with the occipital 
rhombuid, and that it is absent in Chlamydophorus, Tatusia, Cyclothurus, 
Bradypus, Choloepus, in the first two of which the occipital rhomboid 
extends along the meso-scapular spine. 
In reference to the acromio-trachelien muscle, the latter author 
remarks that “the exact relationship of this muscle to the other 
shoulder muscles is not very clear; in the largest proportion of mam- 
mals it is present, and is atlantic in origin and acromial in insertion, 
occupying a position beneath the front edge of the trapezius, but most 
probably, as suggested by many authors, it is a slip of the superficial 
muscular sheet intermediate between the trapezial and cleido-occipital 
factors of that expansion. The elements of this sheet seem thus to be 
trapezius, acromio-trachelien, cleido-occipital, cleido-mastoid, sterno- 
mastoid,” &c. In some cases at least I think we must rather associate 
the acromio-trachelien with the deeper rhomboid stratum with which 
it is sometimes (Pholidotus) evidently fused, and with a greater exten- 
sion of which its absence is occasionally associated ( Notoryctes, Chlamy- 
dophorus). This relationship is well expressed by Cuvier’s appellation 
of “ dorso-trachelien”’ for the three rhomboid factors and “acromio- 
trachelien”’ for the usual omo-atlantic muscle. Leche regards it as 
akin to the levator-scapule group.$$ 
In Chrysochloris||\| the acromio-trachelien is present as a double 
*iv., page 3. txxvi., page 726. {xxix., page 154. §xxxvi., page 106. 
| vi. Pl, 266, fig! 2. ‘Sl xxxvii., page 23. **xxxix:, page s8s.077 las 
page 13. {}xxvii., page 238. §§cf. xxvi., 732. ||| xxvi., page 727 and 
733. 
