318 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.\l. 



"malar" — the first by a diminutive "ball and socket" joint articulated 

 in the usual manner. The " malar," as we know, is the mid-style of the 

 ''infraorbital bar" — the maxillary completing the connection anteriorly, 

 and although upon superficial inspection of this striking ornithic feature 

 of the lateral aspect of the skull, it seems to be firmly united in its schin- 

 dylesial articulation, it simply requires ordinary maceration in the adult 

 of any of the Grouse or Quails to have the three styles separate from 

 each other and from their tympanic and intermaxillary connections. 



The lower jaws of the Tetraoninw are singularly alike in all their 

 characteristics throughout the sub-family. The single bone is devel- 

 oped in the usual way by confluency of the " articular," " surangular," 

 "angular," and " splenial" elements jiosteriorly, and the outer moiety by 

 the " dentary " element, the haemal spine. (Plate Y. See explanation 

 of i)lates for the above described bones.) 



The mandible in the adult has a gentle and increasing curvature 

 downwards from the interangular vacuity forwards. The curvatures 

 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 j)neumatic foramen at the 

 ends of their in-pointed and blunt extremities, and sharp recurved \)V0- 

 cesses behind, in a line with the rami of the jaw, which apophyses long 

 remain in cartilage in immature birds. (Plate X, Fig. 71.) 



On the lateral aspect of the bone, two muscular lines lead away from 

 the coronoidal elevations. These last two mentioned features are univers- 

 ally characteristic of the Tetraonidce ; they are strongly marked in Lag- 

 opus. (Plate XIII, Fig. 88.) Minute foramina are found above and 

 below near the dentary margins, and two quite prominent, one beyond 

 the ramal fenestra 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 markedly 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 Odontophorince is 

 greater, owing to the greater width of the skull when compared with its 

 length. 



In some fine specimens of Lophortyx Calif ornicas, generously furnished 

 us by Mr. Charles A. Allen, of Xicasio, 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 com- 

 mon Virginia Partridge and others. The deflection of the rami anteri- 

 orly is greater in these birds also, or at least more sudden, and so prom- 

 inent are these ramal borders that the inner sides towards the i)osterior 

 ends are converted into true fossae. 



