236 ; MEMOIRS OF THE CARNEGIE MUSEUM 
orbitosphenoids. ‘The presphenoid or rostral portion is thin, occupying a vertical 
plane and forming a portion of the inner wall of the orbital cavity. The basisphe- 
noid on either side sends downward and forward a remarkable long basipterygoid 
process and above these on either side sends out a flat lateral process which fuses 
with the lower wing-like processes of the exoccipitals and the alisphenoids at their 
point of conjugation. 
i ey) |POE 
Vi) ~ 
Y aa Wi 
Y Z ; Fil XY ae 
\\\ _S@ \ 
- 
YY 
Fic. 8. Anterior view of posterior part of skull of Diplodocus (No. %92, Car. Mus. Cat. Vert. Fossils, one half 
natural size). P.F., prefrontals; &.F., right frontal; L.F., left frontal; PO.F., postfrontals ; P.OR., postorbitals ; 
SQ., squamosals ; P.OC., paroccipital processes of exoccipitals ; BS., basisphenoid ; BO., basioccipital processes ; BP., 
basipterygoid processes ; &., rostral portion of basisphenoid ; orb.sph., orbitosphenoids ; al.sph., alisphenoids; J., 
olfactory lobes; JJ., optic foramina; J//., oculomotor foramina; V., trigeminal-foramina ; 1, eustachian foramen ; 2, 
foramina for anterior carotid arteries ; 3, posttemporal fossz. 
The Alisphenoids (Figs. 8-6, 8, and 10).— The alisphenoids articulate dorsally 
with the frontals, postfrontals, postorbitals, parietals and exoccipitals ; posterolater- 
ally with the expanded wing of the exoccipitals where notches are formed on the 
line of conjugation for the exit of nerves, and anteriorly with the orbitosphenoids, 
at the line of union with which notches are likewise formed for the exit of nerves. 
The Orbitosphenoids (Figs. 3, 5, 8, and 10).— The orbitosphenoids are paired 
meeting on the median line above the rostral prolongation of the basisphenoid. 
They articulate dorsally with the frontals and nasals, laterally with the alisphenoids, 
below with the basisphenoid. On the line of conjugation with each other notches 
are formed for the exit of nerves. 
