SHUFELDT.] OSTEOLOGY OF THE TETRAONIDE. 669 
at the extremities of the symphysisial suture are both parabolic, the 
inner being the more open of the two. The interangular fenestra is a 
flattened ellipse, which has distinct sutural traces leading from it, indi- 
cating the borders of some of the original bits of bone of which it is 
composed. 
The “coranoids” are but feebly developed and the articular ends not 
far below them; these latter have the usual pneumatic foramen at the 
ends of their in- 
pointed and blunt << ar aS 17044 ¢ 
extremities, and “~~ FESS, 
sharp recurved pro- 
cesses behind, in a 
line with the rami of 
the jaw, which apo- 
physes long remain 
in cartilage in imma- 
ture birds. (Plate 
X, Fig. 71.) 
On the lateral as- 
pect of the bone, two 
muscular lines lead 
away from the coro- 
noidal elevations. 
These last two men- , 
tioned features are 
universally charac- 
teristic of the Tetra- 
onide; they are 
strongly marked in CD: as. 
Lagopus f (Plate Cupidonia eupido. 
XIII, Fig. 88.) Minute foramina are found above and below near the 
dentary margins, and two quite prominent, one beyond the ramal fen- 
estra on the inner surface of the jaw; still another just anterior to a 
small tubercle below the coronoids on the same aspect. The inferior 
ramal borders are smooth and rounded, as are the under surfaces of 
the articular ends where they originate in nearly the same plane. 
The divergence of the ramal limbs of the mandible in Ortyginw is 
greater, owing to the greater width of the skull when compared with its 
length. 
In some fine specimens of Lophortyx californica, generously furnished 
us by Mr. Charles A. Allen, of Nicasio, Marin County, California, we 
note the striking departure from the mandible in the Grouse in the 
absence of the interangular vacuity—this feature obtains, however, in 
the common Virginia Partridge and others. The deflection of the rami 
anteriorly is greater in these birds also, or at least more sudden, and 
so prominent are these ramal borders that the inner sides, towards the 
posterior ends, are converted into true fosse. 
Those interesting osseous and diminutive oblong plates, the sclerotals, 
present in all of the class, we believe without po ooo are found here 
occupying their usual position. (Plate V, Fig. 51, 2, and Plate X, Fig. 
75, in Cupidonia.) They number from thirteen to eighteen or twenty, 
and their function is so well known that it will not be dwelt upon 
here. They differ principally in the amount of tenacity with which they 
retain their normal relation after prolonged maceration. Cupidonia 
holds a high place here, and the fact seems to be due to the greater 
overlapping of the edges of these little affairs and the toughness, or” 
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