407

377

sternal groove. The length of the bone which includes the beginning of this expansion
is 3 inches 6 lines : the entire bone would be about 4 inches 6 lines in length. The
extreme breadth at the middle of the shaft is 4 1/2 lines. It is thus weaker and more
slender than in Cereopsis, and longer in proportion to its sternal breadth than in
Tachyeres. It also differs from the coracoid in these and other Lamellirostrals in
the very slight production of the tuberosity c in advance of that (b) supporting the
the * articular surface (a) for the humerus. The tuberosity c is divided from b by a
shallow groove (d) of less than half the width of the homologous one in Cereopsis ; and
the tuberosity b is not present in Cereopsis, or is represented (as in fig. 8, b) only by
the produced margin of the relatively larger and deeper facet for the humerus. The
process (e) joining the median facet of the scapular articular expansion is more produced,
more terminally expanded, both lengthwise and transversely ; the latter expansion
inclines, as a curved lamella, toward the inner or anterior division of the tuberosity c,
in advance of the humeral joint.

From the low scapular process in Cereopsis (Pl. CIII. fig. 8, e) a ridge of bone
(ib. f) extends down to the middle of the coracoid, where it blends with the mesial
border, leaving a narrow oblong interspace, 4 lines in length, near that border. This
character is not present in the coracoid of Tachyeres. Such a vacuity (ib. fig. 5, f)
exists in the coracoid of Cnemiornis ; but its filamentary boundary is not continued
from the scapular process (e, e') ; it forms part, or is a continuation, of the sharp
mesial border of the shaft of the bone ; and the vacuity is a perforation of such
border.

An intermuscular ridge (ib. fig. 5, g) is continued in Cnemiornis more directly from
the tuberosity (c), but sooner subsides upon the shaft than in Cereopsis ; it is resumed
at the lower third of the shaft, but nearer the lateral border, and bounds the fore part
of a flat, roughish, elongate tract, which has a continuation of the lateral border (ib.
fig. 7, j) for its hinder boundary. Above this tract, the shaft of the coracoid is thicker
in Cnemiornis than in Cereopsis and other Anserines. The hind surface of the sternal
half of the coracoid is feebly concave ; the sternal articular expanded end had been
broken away in my specimen.

Although this coracoid is more slender, in proportion to its length, than in Cereopsis,
it is thicker, and less flattened from before backward toward the sternal expansion.
This proportion is still more characteristic of the coracoid of Cnemiornis, in comparison
with that of Tachyeres, in which the whole shaft is more flattened than in Cereopsis.

The strength of the bone in Cnemiornis relates to its office in depressing the sternum
in the respiratory movements of the bird.

In describing the humerus (ante pp. 242, 243) forming part of the collection of
bones including a skull of Dinornis robustus and part of one of Aptornis, together with
the tibia and other bones on which was founded the genus Cnemiornis, I stated that,
"from the feeble development of its proximal processes," such as humerus "had evi-