HOLLAND: THE OSTEOLOGY OF DIPLODOCUS MARSH 233 
upper enlargement of the paroccipital process which assumes the form of a smaller 
lateral blunt process directed outward and downward. The squamosals are thin at 
their lower curving ends, where they articulate with the inner surface of the quad- 
rates, which at their upper end are.wedged in between the paroccipitals and the 
postorbitals. 
Fia. 5. Lateral view of the posterior portion of the skull of Diplodocus (%°7, Car. Mus. Cat. Vert. Fossils, one 
229) 
half natural size). 0.¢., occipital condyle ; ex.0., exoccipital ; p.o., paroccipital process of exoccipital ; sg., squamosal ; 
par., parietal ; po.f., postfrontal ; f. frontal; p.f., prefrontal ; p.vr., postorbital ; 0.s., orbitosphenoid ; alsp., alisphe- 
noid ; J o., basioccipital ; b.sp., basisphenoid; b.o.p., basioccipital process ; b.pt., basipterygoid process ; R., presphe- 
noid or rostral part of basisphenoid ; O/., exit of olfactory nerves ; //., optic foramina ; Z//., oculomotor foramen ; V., 
trigeminal foramen ; 7X., glossopharyngeal foramen ; XJJ., hypoglossal foramen; a.c.a., foramen for anterior carotid 
artery ; p.c.a., furamen for posterior carotid artery ; fo., fenestra ovalis; s.g., stapedial groove; 1, small foramen, 
possibly for vein. 
The Frontals (Figs. 8, 5, 6, 8, and 10). — The frontals are paired, and united on the 
median line of the skull by a strongly toothed suture, extending in the specimen 
No. &%& (Carnegie Museum Catalogue), from the point of union with the nasals to 
the parietals. The frontals over the orbital cavity are thick and heavy, measuring 
fully 1.5 em. in thickness. They overlie the parietals posteriorly, and the nasals 
anteriorly, being bevelled in opposite directions on the lower side of the posterior 
and anterior margins for commissure with these bones. Each bone, viewed from 
aboye, sends out a short narrow anterior process at the point where they unite on 
the line of the median suture (Fig. 6, 4), and, another very long and broad process 
projecting forward, outward, and at its extremity downward (Fig 6, 5). This process 
