2 0. C. Marsh—New Family of Dinosaurs. 163 
leaving a large unossified space posteriorly. Above, it meets 
the nasal and prefrontal bones. ong its inner border for 
nearly its whole length, it unites with the ascending process of 
the premaxillary. Hach maxillary contains nine teeth, all 
situated in the anterior part of the bone (Plate III, figure 1). 
_ Along their upper margin, on the inner surface, the maxilla- 
nies send off a thickened ridge or process, which meets its fel- 
low, thus excluding the premaxillaries from the palate. Above 
this, for a large part of their length, the ascending processes of 
the maxillaries underlap the ascending processes of the pre- 
maxillaries, and join each other on the median line. 
The orbits are situated posteriorly in the skull, being nearly 
over the articulation of the lower jaw. They are of medium 
size, nearly circular in outline, their plane looking outward and 
slightly backward. No indications of sclerotic plates have 
been found either in Diplodocus or the other genera of Sauropoda. 
The Supra-temporal fossa is small, oval in outline, and 
directed upwards and outwards. The lateral temporal fossa is 
elongated, and oblique in position, bounded, both above and 
elow, by rather slender temporal bars. 
The pre-frontal and lachrymal bones are both small, the 
suture connecting them, and aiso that uniting the latter with 
the Jugal, cannot be determined with certainty. | 
he post-frontals are tri-radiate bones. ‘The longest and 
most slender branch is that descending downward and forward 
er connection with the jugal; the shortest is the triangular 
Projection directed backward, and fitting into a groove of the 
Squamosal ; the anterior branch, which is thickened and ru- 
gose, forms part of the orbital border above. : ee 
"he squamosal lies upon the upper border of the par-occipi- 
tal process. The lower portion is thin, and closely fitted over 
the head of the quadrate. 
‘he .quadrate is elongated, slender, with its lower end 
Projecting very remarkably forward. In- front, it has a thin 
ete extending inward, and overlapping the posterior end of 
€ pterygoid. ee 
. 1€ quadratojugal is an elongate bone, firmly attached pos- 
'erlorly to-the quadrate by its expanded portion. In front 
Ms the quadrate, it forms for a short distance a slender bar, 
Which is the lower temporal arcade. 
The palate is very high and roof-like, and composed chiefly 
of the pterygoids. “The basi-pterygoid processes are elongate, 
much more so than in the other genera of Sauro, eae 
hy he pterygoids have a shallow cavity for the syne as 
these processes, but no distinct impression for a umella. 
