of Human Monstrosity. 223 



frontal bones : that which is above the less perfect face being much 

 smaller than the other, and formed of one portion only, whereas the 

 other, as is more common, is formed of two. Plate 12. Fig-. A, B, C, D. 

 It is interesting- to determine in what way the bones of the 

 two crania are modified and connected so that two faces may be 

 formed in planes parallel to that of the spines. To this we 

 shall be led by a consideration of the common basis of the 

 crania. Plate 13. Fig. K and L. 



The occipital, basilar, and temporal bones are naturally con- 

 nected on either side, and except that the squamous portions 

 of the latter are very small, and the petrous portions very large, 

 present nothing remarkable. The sphenoid is connected by its 

 body behind to the basilar bone, by its great ahe to the anterior 

 edge of the petrose and squamous bones, and by its ingrassial 

 processes to the frontal bones in the normal condition. And these 

 connexions, of course, prevail here also. But from the smallness 

 of the squamous bone, the alae of the sphenoid are thrown into 

 a direction much posterior to what is their usual direction. The 

 same disposition occurring with respect to the sphenoid of the other 

 foetus, the bodies and two great alae, on opposite sides, oppose 

 each other; a space intervening which is nearly quadrangular. 

 This space is occupied by the united ingrassial processes of op- 

 posite sphenoids closely compressed, (and therefore united by 

 ossific matter) between the right great ate of one, and the left 

 of the other. The great alae and bodies are also united behind 

 these processes from pressure; and, the bodies still maintaining 

 their natural connexion with the basilar bones, thus surround 

 a central space which is oval in form, is covered by fibrous 

 membrane, and is exactly above that common cavity into which 

 the two mouths open. 



