326 MR. W. K. PARKER ON THE STRUCTURE AND 
glenoid facet the squamosal is strongly sutured to the alisphenoid (a/.s.) and to its great 
expanded wing (é.pq.). ‘Together, the zygomatic elements make a strong, deep, and 
convex arch on each side, which starts rather sharply upwards. 
‘The tympanic (ty.), now like a large filbert in form and size, although snaggy and 
ridged below, is principally a mass of square-chambered diploé. It has a small cavity, 
to the produced edge of which the membrana tympani is attached; and its former 
“crura” have met, run upwards, and formed the curious, ascending, coral-like meatus. 
The flange of the anterior crus is now a squamous process beneath the squamosal, and 
close to the inner edge of the glenoidal cartilage. As there are no proper “ foramina 
ovalia” in the posterior sphenoid, so there isa continuous “ foramen lacerum” round the 
tympanic, and between it and the basis cranii (Plate XXXVI. fig. 4, f.l.p.). Looking 
through these large chinks we can see a small part of the periotic mass, which is very 
separate from the surrounding parts. ‘The great occipital plane (Plate XX XVII. fig. 2, 
8.0., €.0., b.0.) is scooped above (s.o.), and then the bone bends forwards, wedging itself 
in between the parietals: the upper element is alate above, and then narrows in and 
rests obliquely upon the exoccipitals (¢.0.), forming the keystone of the archway for the 
medulla spinalis, the foramen magnum (f:m.). The arch again expands its sides, the 
exoccipitals spreading out behind and over the mastoids, which further outwards are 
of the squamosal. These lateral 
) 
plastered over by the “ posttympanic processes’ 
pieces run downwards as the long paramastoid, or, more correctly, paroccipital spurs ; 
whilst their middle region juts out, and forms the diverging, semioval, subpedunculate 
articular condyles (0c.c.). Inside the paroccipital process there is a considerable fora- 
men for the hypoglossal nerve (Plate XXXVI. fig. 4,9). In front of the paroccipital 
process there is a canal, bounded on the outside by the posttympanic spur of the 
squamosal, and on the inside by the unciform tympanic. Looking up this canal we 
see that its inner half is occupied by a rod of bone, thickest below, where it is flat, the 
continuing cartilage being macerated off. This rod is the apex of the stylohyal 
“tympano-hyal” (FLOWER), and the open tube is the canal for the portio dura; its 
mouth is the *‘ stylo-mastoid foramen.” 
The basioccipital (Plate XXXVI. fig. 4, b.0.) is a pentagonal lozenge of bone, joining 
the sides of its own arch by suture, and separated from the next basal piece (d.s.) by a 
narrow synchondrosis. This basioccipital plate is mammillate at the sides below, and 
subcarinate mesially: it is the notochordal bone. Next in front is the basisphenoid 
(Plate XXAVI. fig. 4, .s.), now merely the basal part of an inverted arch of bone, the 
“posterior sphenoid.” ‘The narrow cartilaginous tract between this and the bar in front 
is hidden below by the end of the vomer, and by a sharp ridge which grows mesiad 
from each alisphenoid (Plate XXXVI. fig. 4, al.s., 0.s.,v.). The orbito-sphenoids have 
met below, ossifying the underlying trabecular bar, which part is ensheathed by the 
vomer. ‘These large wings can be seen in the posterior part of the orbit around and 
above the optic foramen (Plate XXXVIL. fig. 1, 0.8.2), and also from behind through 
the foramen magnum (Plate XXXVII. fig. 2, 0.s.,2). The change which has taken 
