268 ZAGLOSSUS. 
medially from the manubrium to the large third sternebrum. Its fibers pass like- 
wise in a stout bundle to an insertion on the pectoral ridge of the humerus, 
slightly posterior and lateral to the insertion of the ectopectoralis. In the Echidna 
the separation of the ectopectoralis from entopectoralis seems much less clearly 
marked, if indeed, it is to be distinguished at all. A third portion seems to 
represent a xiphihumeralis. It arises as a narrow muscle at the median line, 
from the xiphisternum, whence it extends posteriorly about 25 mm. It passes 
obliquely forward and inserts on the pectoral ridge at the caudal end of the 
greater tuberosity of the humerus. 
In addition to these, there is a large muscle that arises along the entire 
anteroventral edge of the clavicle from the articulation with the scapula 
nearly to the median line. Its insertion is likewise on the pectoral crest con- 
tinuous with and slightly anterior to that of the entopectoralis. This muscle 
both Mivart and Westling find in the Echidna. The former considers it a part 
of the deltoid on account of its proximity to the acromion at the dorsal point 
of origin. This interpretation is accepted with some misgiving by Westling, 
who suggests that it may almost equally well represent a clavopectoralis, a view 
that seems quite as probable. 
The abdominal muscles present no special peculiarities, but are essentially 
similar to those of the Echidna. The rectus abdominis is a strong band of muscle 
fibers some 20 mm. wide, from the base of the epipubic bone passing forward 
on each side to insert on the ventral prominence of the coracoid and on the 
ventral half of the first rib. 
The obliquus externus is strongly developed, and overlies the posterior 
half or more of the preceding muscle. It arises from the anterior edge of the 
pubis and the epipubic bone, the tuberosity of the ium and the lumbar verte- 
brae, and by a series of muscle strips from the second to the last rib. Each of 
these strips arises just proximal to the union with the sternal portion of the rib- 
and hence the origins become successively higher dorsally, in passing posteriorly. 
These strips are all united by fasciae, and between the pubis and the thoracic 
basket the muscle forms a continuous sheet of fibers, that becomes thickest 
over the abdomen and is joined as usual to the corresponding muscle of the 
opposite side. 
The obliquus internus is in intimate connection with the fibers of the trans- 
versus abdominis from which it is hardly to be separated. The latter is likewise 
closely connected with the obliquus externus along the lumbar and pelvic origin. 
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