MR. ST. G. MIVART ON THE ANATOMY OF ECHIDNA HYSTRIX. 401 
articular cavity and to the bone generally (both coracoid and ischium being posterior in 
position) also the suprascapular notch seems to repeat the sacro-sciatic one, while the 
spine of the ischium, with the lesser sacro-sciatic ligament attached to it, recalls to 
mind the prominence from the base of the coracoid with its coracoid ligament, which 
prominence becomes so much developed in certain mammals, 
As to the spine and acromium of the scapula, there appears, on this view, to be 
nothing to represent them in the ilium, unless it might be the ilio-pectineal line and 
eminence, though the latter seems to be rather a development from the pubis than from 
ihe ilium. These osteological resemblances between the scapula and ilium I mention 
only as suggestions, being myself as yet far from convinced of their validity. 
Dr. Humphry and, long before him, Vieq d'Azyr have both recognized the cor- 
respondence between the anterior border of the ilium and the axillary margin of the 
scapula; they both, however, take for granted that the subscapular fossa answers to the 
iliac one. 
Now, in the Echidna as has been said, the surface of the scapula which gives origin 
to the subscapularis looks backwards and outwards. Are we, then, to regard the scapula 
in that animal as being, so to speak, in a more normal and natural position than that 
of most mammals, or, on the other hand, as being modified in a special and peculiar 
manner? Possibly the latter. For, in fact, the scapula is in that animal so formed 
that the middle of its outer surface (the point of origin of the triceps) might be con- 
sidered to correspond to the axillary margin of the scapula of an ordinary mammal, 
and the anterior margin (superior costa of Man) to represent almost, if not quite, the 
actual posterior margin of the scapula of the Echidna. 
In the Ornithorhynchus the conditions are somewhat different ; for though the scapula 
is turned forwards, yet part of the subscapularis occupies a portion of the inner or costal 
surface of the scapula, while the supraspinatus muscle seems to be of much less 
extent. 
On the whole, I am inclined to believe that extended investigations will show that the 
scapula and ilium may most conveniently be regarded as, so to speak, essentially co- 
lumnar bones, such as we find them in Chelonians, and serving to give origin to muscles 
inserted into the proximal bone of each limb, but varying in shape and size, and de- 
veloping ridges or processes according to the exigencies of each case’. In most mammals 
a large lamella of bone is shot out between the supra- and infraspinatus, another be- 
tween the supraspinatus and subscapularis, and another, still larger one between the 
last-mentioned muscle and the infraspinatus. i 
. In the Ornithorhnychus we might consider the plate between the infraspinatus and the 
subscapularis to be suppressed, and that between the supraspinatus and the subscapular te 
to be almost so. On the other hand, that there is a plate developed opposite to that 
separating the supra- from the infraspinatus musele, which, as it were, passes into the 
midst of the subscapularis, throwing the posterior part of it to the outside and on to 
' I am very happy to be able to add that my friend Mr. W. K. Parker has informed me that he has independently 
arrived at a similar conclusion, having been led to it by his osteological investigations. 
