Dion MEMOIRS OF THE CARNEGIE MUSEUM 
extremities with the quadrate bones. Their ends project slightly beyond the quad- 
rates, and the posterior and marginal surfaces reveal provision for strong muscular 
attachments. They articulate below with the basioccipital and above this on either 
side by a wing-like process with the alisphenoid, the lower portion of the wing of 
which meets and overlaps the wing of the exoccipital. On either side of the supra- 
occipital they articulate with the parietals, and beyond these touch the squamosals 
along the proximal portions of the inferior margins of the latter bones. In front on 
either side they articulate with the alisphenoids. 
The Supraoccipital (Figs. 3, 4, and 6).— The supraoccipital is a comparatively 
small bone, rudely defined as quadrilateral in outline viewed from behind, which 
is wedged in between the exoccipitals and the parietals. Its posterior surface is 
produced as a strong process at the middle of the occipital crest for the attachment 
of the nuchal ligament. Its upper anterior portion in specimen 4% (Carnegie 
Museum Catalogue) appears to advance for a short distance on the median line be- 
tween the parietals, and is more strongly advanced in specimen No. 694 (Cat. Am. 
Mus. Nat. Hist.). (See Plate XXVII., Fig. 2.) _ On either side of this point in the 
specimens which the writer has ‘examined it appears to be wedged in underneath 
the parietals, articulating with them by irregular rugose surfaces. 
The Parietals (Figs. 83-6). —'The parietals are small bones placed one on each 
side of the occipital crest, their outer surfaces constituting the lateral portions of 
this crest. They articulate posteriorly with the supraoccipital near the median line 
of the skull and beyond this on either side with the exoccipitals. At their outer 
extremities they articulate with the squamosals, the upper edge of the alisphenoids, 
and the postfrontals. (See Fig. 5.) In front they articulate with the frontals. 
Concerning their relation to the pineal foramen the writer will have some observa- 
tions to make elsewhere. (See p. 243.) 
The Squamosals (Figs. 8-6 and 8-9.) —The squamosals are hook-shaped bones 
curving outwardly and downwardly, forming with the upperjantero-external portions 
of the exoccipitals the posterior upper wall of the supratemporal fossa, which is rela- 
tively small, and, as Professor Marsh has described it, ‘oval in outline, and directed 
upward and outward.” The squamosals articulate on the inner portions of their 
inferior margins with the paroccipital processes of the exoccipitals. The outer por- 
tion of their inferior margins is free for about half the length of the bone forming 
the upper margin of the posttemporal fossa which Professor Marsh * in the case of 
the skull of his so-called Atlantosawrus denominates ‘the posterior fossa,” and which 
at its upper end is bifid, as in Atlantosawrus, owing to the projection into it of an 
3 Dinosaurs of North America, Pl. XV., Fig. 1. 
