PROFESSOR OWEN ON THE GENUS DINORNIS. 389 
§ 8. Larynx of Dinornis crassus? 
The portion of a thin, hollowed, shield-shaped piece of bone (Pl. XLVII. fig. 8, a, 4) 
I take to belong to the upper larynx, and to be part of the thyroid element. To its 
lower border has coalesced, as is sometimes found in existing birds, the first tracheal 
bone or hoop (¢), which, as usual, is incomplete; the coalescence is limited to the two 
ends of this half ring; the slit of separation between it and the thyroid is 9 lines in 
extent, giving the breadth of this slender bone as half a line; it projects anteriorly 
like a folded lower border in advance of the actual lower border of the thyroid, which 
is the more prominent part on the inner or concave side of the thyroid. One might 
expect the rings near to or following this to have similar slender proportions, like those 
worked out of the matrix beneath the skull of Dinornis crassus; lower down the wind- 
pipe they gained in depth. 
From another mass of matrix, exhibiting a portion of a broad tracheal ring, I worked 
out the part of the expanded terminal one, to which, in the entire or recent state of the 
parts, the bronchi are attached; it answers to that supporting the cross bar shown at 
t, fig. 103, ‘ Anatomy of Vertebrates,’ vol. ii. p. 222, in the Raven, and ranks among the 
parts of the lower larynx. The specimen shows the contiguous portions of two cavities, 
meeting at a sharp straight ridge (fig. 9, @), 8 lines in extent, which was produced into 
the cavity of the trachea, dividing the tube from before backward; the concavities on 
each side are the beginnings of the divisions or the continuations of the trachea into 
the bronchi. The margins of the expanded bone, continued from one (probably fore) 
end of the dividing ridge, are rather thickened. Cemented by the matrix to this part 
of the lower larynx was one, probably the first, of the bronchial bones (fig. 9, 4c); it is 
incomplete, varying in breadth from 2 lines to nearly 3 lines, and may have surrounded 
two-thirds or three-fourths of the bronchus. At the broader part the outer surface is 
rather convex from the upper to the under margin; at the narrower part this surface 
is concave. It seems to answer to that part of the lower larynx figured at a, fig. 103, 
tom. cit. p. 222. 
§ 9. Trachea of Dinornis rheides ? 
To a smaller species of Dinornis, probably D. rheides, I refer a series of rings, about 
80 in number, similar in shape and general character to those of Dinornis crassus, but 
of a smaller size (Pl. XLVII. figs. 10-12). 
The range of variety of size is here rather less. The largest ring yields, in long 
diameter, 9 lines, in short diameter 7 lines (fig. 11); the smallest gives 7 lines and 6 lines 
in the same diameters (fig. 10). The average, or common size, is 8 lines in long and 62 
in short diameter (fig. 12); the ellipse is more perfect and constant in the rings of this 
species, and the concavity from edge to edge of the outer surface of the hoop is more 
constant and more marked than in Din. crassus. The depth of the hoop is greater, 
VOL. VII.—PaRT v. January, 1871. 3H 
