3n2 PROCEEDINGS OF THE CANADIAN INSTITUTE. 
structures lying above it. The lines of attachment may be under- 
stood from Fig. 7. 
It is necessary to look more closely at the connections of the 
malleus. As observed above it articulates in an oblique groove on 
the side of the third vertebra. Outside this point its upper surface 
is connected by ligament with the ventral face of the fourth trans- 
verse process, and its postero-external angle here passes into the 
crescentic ossification (co), which may be described as the posterior 
sickle-shaped part of the madleus, although it is not developed as a 
part of the third transverse process. It is in fact an ossification in 
the tunica externa of the air-bladder, and only secondarily becomes 
connected with the third transverse process. A sharp ridge separates. 
these anterior and posterior parts of the malleus. The dorsal and 
lateral limb of the crescent rests on the ventral face of the fourth 
transverse process, while its ventral and medial limb rests on a 
groove on the sides of the body of the fourth vertebra. 
In the concavity of the crescent, and connected with it in the 
recent state by fibres of tendinous lustre, is the thickened knob-like 
end of an oblique ossification (0.0) which is free from the body of 
the vertebra, but becomes coalesced as it runs backwards and out- 
wards with the posterior part of the ventral face of the fourth 
transverse process. Between the body of the vertebra and this 
oblique ossification is a triangular space in which lies the vena cava 
inferior. The course of this vessel is ventral to the origin of the 
third and fourth transverse processes, but dorsal to both the oblique 
and crescentic ossifications, the intervening space being larger on the 
right than on the left side to accommodate the larger vessel. 
Across the posterior part of the triangular space described the 
upper end of the flat band is attached. All the dorsal median wall 
of the anterior chamber is likewise firmly bound down to the sides. 
of the bodies of the fourth and fifth vertebrae, and especially to the 
sharp ridges bounding the aortic canal. Further forwar s also, the 
dorsal wall is attached to the sharp ridge separating the third and 
fourth vertebre by strong fibres to the knob of the oblique ossifica- 
tion, and to the ventral edge of the thickened anterior part of the 
fourth transverse process. 
The fibres of the unattached parts of the anterior chamber chiefly 
converge (1) from the anterior wall to the crest separating the anterior 
and posterior parts: of the malleus, and (2) from the rest of the 
