270 ZOOTOMY. 



In the adult, the basi-, ex-, and supraoccipitals are all 

 fused together into the single occipital bone. 



45. The interparietal, a small transversely oval bone, 

 interposed between the middle part of the front edge of the 

 supraoccipital and the parietals (§ 46). 



46. The parietals, a pair of thin, slightly arched bones, 

 forming a considerable part of the roof of the brain-case : 

 they are separated from one another by the median sagittal 

 suture, and from the interparietal and supraoccipital, with 

 which they articulate posteriorly, by the transverse lamb- 

 doidal suture : the outer edge of each gives off a long 

 downwardly directed process, which, in the entire skull, is 

 covered by the squamosal (§ 53). 



47. The frontals, roofing in the anterior part of the 

 brain-case, articulated with one another in the middle line 

 by the frontal suture, and with the parietals behind by 

 the transverse coronal suture. Each is an irregular bone, 

 with a slightly arched upper surface ; an irregular anterior 

 border ; an orbital process, a thin plate continued down- 

 wards and inwards from its outer border, and forming the 

 upper part of the inner wall of the orbit ; and a supra- 

 orbital process, projecting directly outwards from the 

 outer border, free at both ends, and forming a protection to 

 the orbit above. 



48. The basisphenoid, articulated behind by a broad 

 surface with the basioccipital, and tapering in front to a 

 blunt point ; it is perforated at about the middle of its 

 extent by an oval foramen, and its upper surface is hollowed 

 out to form the sella turcica, which lodges the pituitary 

 body (§ 484), and is bounded before and behind by the 

 anterior and posterior clinoid processes, of which 

 the latter only are formed by the basisphenoid. 



49. The alisphenoids : two wing-like bones directed 



