134 
PROFESSOR A. MACALISTER ON THE 
portionally in Noctulina. In the Pteropine Bats it is of very large size, especially in 
Cephalotes ; in Megaderma lyra ancl Pteropus edulis it shows a very remarkable and 
interesting feature, namely, a tendinous inscription obliquely crossing it opposite the 
angle of the jaw. This is very interesting in a morphological point of view, as the 
muscle is not protracted further forward than usual in these species ; it shows that the 
two bellies of the truly digastric type of depressor of the mandible (such as is found 
among the Primates and the Eodentia) are represented in this and other orders by the 
single-bellied muscle, and that it is not simply a homologue of the posterior belly. 
Thus from the single-bellied muscle of the Carnivora and Cetacea &c., we have the 
intermediate step of the digastric intersected by an inscription leading us to the truly 
biventral form in the higher mammals. 
The omo-hyoid is a slender and distinctly biventral muscle in the Vespertilionidse. 
In the Phyllostomine Bats it is large, and with scarcely any trace of a tendinous inter- 
section. In Macroglossus it passes from the suprascapular ligament to the hyoid bone, 
and, as in the other Pteropine Bats, it is digastric, but its central tendon is very short. 
In my specimen of Noctulina there is a muscular band arising from the middle of the 
clavicle and joining the sterno-hyoid muscle at a point about midway between the origin 
and insertion of that muscle ; immediately beyond the point of union a tendinous line 
existed in the combined sterno-hyoid and omo-hyoid muscles; no other omo-hyoid 
existed in this species, and this arrangement was present on both sides. This method 
of attachment in the omo-hyoid has hitherto only been known as an anomaly in human 
anatomy, and as such I have described it (Trans. Royal Irish Academy, vol. xxv. 1871, 
p. 22). 
The three scalenes exist in the Bat as Meckel has described. The anterior is very 
small, and in Vampyrops ascends to the transverse process of the second cervical ver- 
tebra ; the medius and posticus are united at their origins, separate at their insertions. 
Meckel says they are arranged as in the Carnivora ; the posticus does not extend below 
the fourth rib. 
The other deep muscles of the neck, longus colli, longus atlantis, recti capitis antici, 
major et minor, displayed no points worthy of special notice. 
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Muscles of the Thorax. 
This group of muscles is of deep interest, as its elements are concerned in the action 
of flying. 
Pectoralis major (Plate XV. fig. 1, s) is in two parts in all species, but they vary 
slightly in their degree of separability ; it is distinctly cleft in the Pteropine Bats into 
a clavicular and a sternal muscle, not quite so separable in the Phyllostomidse, separate 
at origin but combined at insertion in the Plecotus, with little more than a distinct 
trace of division in Vesperugo , and nearly completely severed in Vespertilio , Noctulina , 
and Scotophilus hesperus. The sternal part is undivided and of enormous size, arising 
from the whole length of the sternum, except the xiphisternum, from the anterior 
sterno- clavicular ligaments, and it is inserted into the pectoral crest on the humerus. 
