HOLLAND : THE OSTEOLOGY OF DIPLODOCUS MARSH 237 
The Quadrate (Figs. 3 and 9 and Plate XXIII.).— The quadrate is a long bone 
articulating by its proximal extremity with the ends of the paroccipital processes 
of the exoccipitals, the squamosal, and the postorbital, uniting with these bones to 
form the outer margin of the supratemporal fossa. At its distal extremity it articu- 
lates for about five centimeters with the quadratojugal, under the posterior end of 
which it sends out a hook-like process for support. The quadrate at its lower ex- 
tremity from about the middle broadens inwardly as a thin plate of 
bone, sending a process forward and downward to overlap the pos- 
terior ends of the pterygoid. This thin bony plate in part forms 
the inner lower wall of the infratemporal fossa. 
The Quadratojugal (Fig. 3 and Plates XXIII. and XX VI.).— The 
quadratojugal articulates in the manner already described with the 
Fie. 9.  Tia- 
gram showing the 
quadrate by a flattened enlarged head, underlaid and hung in the _ selation of the bones 
hook-like extremity of the quadrate. The bone narrows below the  4¢ the outer margin 
: - . 9 of the supratem poral 
infratemporal fossa into a comparatively narrow bar, and then widens aie 
; fossa. 1, paroccip- 
to the line of articulation with the jugal and the maxillary. Just ital process of exoc- 
below this union along the outer margin of the upper jaw the  «ipitals; 2, squamo- 
5 pe a 0 sal ; 3, quadrate ; 4 
bone expands and flares out horizontally. The manner of its ar- fees sn 
: postorbital ; 5, post- 
ticulation at both ends is best revealed by specimen No. 2673, U. frontal; 6,supratem- 
S. N. M. (See Plate XXIII.) The specimen (A. M. N. H., No. _ poral fossa. 
969) (see Plate XX VI.) has been restored in such a manner as to fail to show the 
true manner of articulation. 
The Jugal (Fig. 3 and Plates XXIII. and XXVI.).— The jugal is a thin, very 
irregularly shaped bony plate which sends backward a long narrow process to articu- 
late with the anterior process of the postorbital, with which process it unites to 
orm the lower margin of the orbital cavity. Below it sends back another lon 
f the | 2 f tk bital ty. Bel t Is back ther long 
narrow process to articulate with the quadratojugal. Between these two processes 
is a broad sinus forming the anterior margin of the infratemporal vacuity. Above, 
1e Jugal bone sends up a process which articulates with the preorbital at its lower 
the jugal | Is up a | hich articulat th the bital at its lower 
end. ‘This superior process further sends forth a small lateral process directed up- 
ward and forward, and projecting deeply into the posterior portion of the antorbital 
vacuity. The lower portion of the anterior margin of the jugal articulates by an 
irregularly curved line with the posterior border of the maxillary. 
The Nasals (Fig. 3 and Plates XXIII. and XXIYV.).— The nasal bones are paired 
bones somewhat semilunar in shape when seen from above. They are quite thin on 
their anterior margins, thick behind and are convexly bevelled posteriorly in order 
to articulate with the anterior margin of the frontal bone. They articulate also with 
