330 
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 ny the matrix to this part 
of the lower larynx was one, probably the first, of the bronchial bones (fig. 9,4 ¢); 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 
+s concave. It seems to answer to that part of the lower larynx figured at a, fig. 103, 
tom. cit. p. 222. 
§ 5. 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. XCIII. 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 6} 
in short diameter (fig. 12); the ellipse is more perfect and constant in the rings of this 
species, and the concayity 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, 
relatively, and is maintained through a greater extent of the windpipe, as it seems; 
this dimension is 2 lines, with slight change at parts of the circumference. 
Of this species there is one specimen of a sequence of four rings in the same portion 
of matrix (fig 12), another piece with three rings, and three or four with two rings. 
The extreme of depth of hoop is reached at part of the circumference of the ring 
(fig. 11, a, 8). 
§ 6. Trachea of Dinornis elephantopus ? 
The tracheal rings of the third series are remarkable for their great breadth and 
thickness. There are about 80 of these, of a full elliptical, subcireular, or circular 
shape, with an average diameter or long diameter of 9 lines, The specimen figured 
(Pl. XCIII. fig. 13, a, 6) shows the average size or common character of these strong, 
broad, well-ossified tracheal rings. The exterior surface is rugose, the inner one 
smoother, both surfaces straight or even from one margin to the other; the margins 
are flat, as if made by a clean cut, and show regular perforations, probably vascular, 
of the osseous tissue. The thickness of the hoop is rarely uniform, the difference 
being, in several rings, as great as in that figured in 15, @; there is also, occasionally, 
a variety in the breadth at different parts of the circumference of the hoop, though 
rarely to the extent shown in fig. 16, which, from its small size, may possibly be a 
bronchial hoop. 


