t 



252 



recognized at a glance of Plates XXXVI. and XXXVII. The occipital region (Plate 

 X XXVII. fig. 1) represents the upper half of a transverse ellipse, being arched above ; the 

 straight line, or section, below is interrupted by the paroccipitals (<, 4), which descend on 

 each side of the condyles (•.>, »), about 2 inches below the level of the foramen magnum, ; 

 the mastoids {%, ») and squamosals (2;, 27) bound the region externally. The breadth of the 

 occiput at its base is 13 inches, the height at the mid line 7 inches. The surface inclines 

 forward (Plate XXXVI. fig. 1, s) especially at its mid third (Plate XXXVII. figs. 1 & 2, 3), 

 but becomes vertical, or nearly so, as it arches outward. The surface is broadly undulate 

 transversely, being concave at the mid third, convex at the two outer thirds. Nearly the 

 whole of this surface is roughened by ridges and insertional impressions of nuchal muscles, 

 the sharpest and most prominent of which is the medial vertical one (ib. figs. 1 & 2, 3), 

 extending from near the upper border of the foramen magnum to the transverse ridge 

 bounding the occiput superiorly : this ridge describes a low arch transversely ; lengthwise 

 it extends toward the upper surface of the cranium, describing an open angle with the 

 truncate apex' forward (ib. fig. 2). The condyles form the lower two thirds of the fora- 

 men magnum, save at the interval of seven lines between their lower ends (ib. fig. 3, 2, 2). 

 From these they diverge as they rise with a vertical convexity, greatest at the lower 

 half of the condyle, and more gradual toward the upper and outer end. The transverse 

 convexity is more regular, and affects the hinder, outer, and under parts of the joint. 

 The length of each condyle is 2 inches 7 lines, the extreme breadth is 1 inch 3 lines, 

 the distance between the upper ends is 4 inches 6 lines. The surface towards the 

 foramen is almost flat in the least diameter, gently concave or rather undulating length- 

 w i»e. The plane of the occipital foramen is vertical ; its shape is a full ellipse, with the 

 least diameter transverse ; this gives 1 inch 8 lines ; the long diameter is 2 inches. 



A broad groove or channel, directed from below upward and outward, divides the 

 condyle from the base of the paroccipital ( 4 ). This broad process inclines forward before it 

 descends, its hinder plane being anterior to that of the convex part of the occiput above. 

 The obtuse termination of the process is continued, with a curve upward and outward, 

 by a thick and rugged ridge into the mastoid process (s), which, with the squamosal, 

 bounds the occipital region laterally. The outer margin rises from the mastoid with a 

 slight convexity for four inches before curving inward to the upper arch of the occipital 

 ridge. A fracture of the outer table on the right side of the occiput exposes the extension 

 to this part of the cranial walls of the air-cells continuous with larger cavities in advance. 



The base of the huge zygomatic arch is continued (Plate XXXVI. fig. 1, 2;), with a 

 slight sinking inward, from the whole vertical extent of the mastoid ridge and from a 

 part of the superoccipital ; the lower end being formed by the tympanic, which is defined 

 by a slight notch from the end of the mastoid process. 



The parietal walls (ib. 7) extend from without inward and forward. From the short 

 alisphenoid the parietal plate arches upward, with a strong convexity forward at its 

 lower half (Plate XXXVII. fig. 3, 7) ; this subvertical part of the cranial walls forms 

 the hind boundary of the vast subquadrate oblong vacuity combining orbit and temporal 



