326 



ME. W. K. PAKKEE ON THE STEUCTUEE AND 



glenoid facet the squamosal is strongly sutured to the alisphenoid (al.s.) and to its great 

 expanded wing (e.pg.). Together, the zygomatic elements make a strong, deep, and 

 convex arch on each side, which starts rather sharply upwards. 



The tympanic (fy.), now like a large filbert in form and size, although snaggy and 

 ridged below, is principally a mass of square-chambered diploe. 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 is a continuous " foramen lacerum " round the 

 tympanic, and between it and the basis cranii (Plate XXXVI. fig. 4, f-l.]).). 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 XXXVII. fig. 2, 

 €.0., h.o.) is scooped above (s.o.), and then the bone bends forwards, wedging itself 

 in between the parietals : the upper element is alate above, alid then narrows in and 

 rests obliquely upon the exoccipitals (e.o.), 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 

 plastered over by the " posttympanic processes " of the squamosal. These lateral 

 pieces run downwards as the long paramastoid, or, more correctly, ])aroccipital spurs ; 

 whilst their middle region juts out, and forms the diverging, semioval, subpedunculate 

 articular condyles [oc.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, i.o.) is a pentagonal lozenge of bone, joining 

 the sides of its own arch by suture, and separated from the next basal piece {h.s.) by a 

 narrow synchondrosis. This basioccipital plate is mammillate at the sides below, and 

 subcarinate mesially: it is the notovhordal bone. Next in front is the basisphenoid 

 (Plate XXXVI. fig. 4, h.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.., h.s., v.). The orbito-sphcnoids have 

 met below, ossifying the underlying trabecular bar, which part is ensheathcd by the 

 vomer. These large wings can be seen in the posterior part of the orbit around and 

 above the optic foramen (Plate XXXVII. fig. 1, o.s., 2), and also from behind through 

 the foramen inagnum (Plate XXXVII. fig. 2, 0.6'., -'). The change which has taken 



