- 
a2t 
diameter, 7 lines in short diameter; the depth of the rim of the bony hoop varied from 
one line to half a line; its thickness was about a quarter of a line. The outside of the 
ring is convex and finely rugose; the inside is less conyex and smooth. 
I cannot hold it as certain, that, because these slender rings were found at or near 
the position of the upper larynx, therefore they were from the beginning of the wind- 
pipe; for the dislocation of the parts of the skeleton in all the individuals so repre- 
sented in the marshes of Ruamoa, as far as can be gathered from the account given 
by Mr. Mantell, might well admit of displacement of parts of the bony trachea: but I 
think it very likely that they are upper tracheal rings. 
Admitting this doubt as to their precise position in the windpipe, still the proba- 
bility is so great that tracheal rings preserved in contact with parts of the skeleton were 
parts of the same bird, that the rings here described may be reasonably referred to the 
Dinornis crassus. | 
There is, moreover, a significant degree of correspondence between the number ot 
tracheal rings of the type of those attached to the skull, but collected without note of 
precise relations, probably scattered in the matrix, and the number of individuals of 
Dinornis crassus indicated by bones of the skeleton; that is to say, both tracheal rings 
and skeletons or bony evidences of D. crassus are amongst the most plentiful of the 
species there found. 
The rings or hoops, upwards of 150 in number, provisionally referred to Dinornis 
crassus, are associated together by the character of shape and size. Jn general they are 
less slender than those cemented to the skull-base; but they present a certain range in 
the thickness, especially the depth, of the wall of the ring. The extreme of the latter, 
or breadth in the axis of the windpipe, is 3 lines, as at fig. 2, 6, Pl. XCIII.; but this is 
partial, the hoop decreasing to 2 lines and 14 line at part of the circumference, in a 
few at the small ends of the ellipse, or the lateral parts of the hoop; the more common 
breadth is from 2 lines to 14 line (Pl. XCIII. fig. 1, d); those found at the base of the 
skull, and inferred to be from the upper part of the windpipe, were 1 line, decreasing 
partially to $ a line, in depth. There is less range of thickness in the elliptical rings 
of Linornis crassus, as, €. 9. from 7g to $ of a line, seldom getting to % (ib. figs. 1 & 3). 
There is a certain range of size and of shape of the ellipse: thus, in fig. 1, a, 4, excep- 
tional instances of subcircular rings are figured; in fig. 3, a, 6, the long axis is 10 lines, 
the short one 9 lines; in fig. 3, ¢, the long axis is 114 lines, the short one 8 lines. Most 
of the rings have intermediate proportions; in a few the ellipse is less regular, one side 
inclining to flatness. There is a variety also in the configuration of the surfaces of the 
hoop; instead of the outer surface being convex from the upper to the lower margins, 
as in the slender rings detached from beneath the skull, it is flat, especially in the 
broader varieties, in which the inner surface preserves a slight convexity in the same 
course; in some rings the outer surface is slightly concave from edge to edge (as in 
fig. 2, 5). 
