358 PROFESSOR OWEN ON THE GENUS DINORNIS. 
from one to two lines. From this type connexion or origin each arches obliquely 
upward and outward, in a degree increasing from behind forward, where opens the 
base of a semiconical cavity so formed, the thin lamellar wall of which is continued 
down into the posterior one of the palatal nostril. The cavity above this opening is 
divided by a horizontal portion into two culs-de-sac. From the walls of this cavity two 
plates are continued, one median, the other lateral. The median one projecting, where 
the palato-narial cavity begins to expand, from the common posterior plate or body 
of the palatine, descends vertically and abruptly, for 5 lines, gradually losing depth 
and gaining breadth at the level of the roof of the mouth, where it extends forward on 
each side the midpalatal vacuity for about one inch, coalescing with the maxillary, but 
leaving a trace of the original separation ; the median side of the median plate is convex ; 
the outwardly curved free border is somewhat thickened; the outer concave side of the 
plate and the oblique longitudinal channel between the median and lateral descending 
plates of the palatine have a rather rough surface. The outer or lateral lamella, con- 
tinued from the outer wall of the palato-narial cu/-de-sac, extends downward and outward 
in a less degree than does the median plate, and without thickening of the free border, 
but expanding horizontally, as it advances, to coalesce with the base of the malar process 
of the maxillary. The interlamellar channel, with a general breadth of 4 lines, gradually 
deepens as it retrogrades, until the inner plate suddenly ceases; the outer plate then 
contracts, becomes horizontal, and converges to unite with that of the opposite palatine 
behind the palato-nares. The inner wall of the palato-narial cu/-de-sac is continued for- 
ward, contracting to a styliform process, which is, indeed, the fore end of the articular 
origin of the complex cranial pleurapophysis—such origin extending backward, as above 
described, from its own to the succeeding centrum, as the head of a rib is apt to do. 
At the opposite end the palatine, as above described, bifurcates to effect two junc- 
tions with its hemapophysis, the maxillary—one with its outer or dentary border, the 
other with its inner or palatal productions. 
The short maxillary (21) presents or radiates, as usual in birds, its premaxillary, 
palatine, nasal, and malar productions. Posteriorly, between its palatine, nasal, and 
malar rays, it expands into a sort of rudimental “antrum” consisting of two low, 
shallow, pneumatic fossz divided by a horizontal shelf, concave backward ; and from 
the lower division goes a small oblique communication with the fore part of the hypo- 
palatine channel, just showing where the maxillary contributes to and continues the 
fore part of that channel. The small foramen answers to the commonly larger (palato- 
maxillary) vacuity at this part of the roof of the mouth. ‘The nasal process of the 
maxillary preserves part of its posterior margin free; the rest is intimately blended with 
the long maxillary style of the nasal (fig. 1,4) above described. The anterior trans- 
versely expanded part of the maxillary is intimately blended with and contracts above 
to be wedged between the maxillary and palatal parts of the premaxillary. These are 
the true or type beginnings, or basis, of that “ hemal spine.” ‘They speedily coalesce as 
