104 Proceedings of the Eoyal Society of Edinburgh. [Sess. 
failure of the anterior part of the antrum of Highmore to develop. When 
the skull is studied in section it is found that the other air-sinuses are well 
developed. 
The measurements of the skull are given in Table I. 
Table I. — Pkincipal Skull Measurement and Indices. 
Subject A 9. 
Average of Seven 
Irish Skulls 
(Cunningham) (8). 
mm. 
mm. 
Glabello-occipital length . 
174 
189 
Maximum breadth . 
135 
143 
Cephalic index .... 
77 
75-7 
Horizontal circumference . 
504 
526 
Length of foramen magnum 
32 
36*7 
Basi-nasal length 
97 
103 
Basi alveolar length . 
93 
98-6 
Gnathic index .... 
95-8 
95-6 
Interzygomatic breadth 
122 
131 
Intermalar breadth . 
100 
HIT 
Naso-alveolar length . 
68 
73*4 
Facial index .... 
55-7 
56 
Nasal height .... 
36 
53-7 
Orbital width .... 
37 
41 
Orbital height .... 
33 
35T 
Orbital index .... 
89 
85-3 
Naso-mental length 
114 
120 
Table I. {continued). — Dimensions of Mandible. 
Subject A 9. 
Average of Three 
Irish Mandibles. 
mm. 
mm. 
Symphysial height . 
34 
34 
Coronoid height 
70 
67 
Condyloid height 
66 
70 
Gonio-mental length . 
89 
95 
Gonio-alveolar length 
85 
91 
Intergonial width 
85 
100 
Breadth of ascending ramus 
26 
33 
A comparison of the measurements of the skull of subject A 9 with the 
measurements of seven Irish skulls shows that it is small but well-pro- 
portioned. The most striking departure from the normal is the extreme 
shortness of the intermalar breadth. 
This is due to the small development of the maxillary antrum, which 
also reduces the naso-alveolar length. 
