68 THE SKELETON 



superior surface lies flattened against the under surface of the pre-sphenoid, whilst the base of 

 the cone is in contact with the lateral mass of the ethmoid. 



The deposits of earthy matter from which the sphenoidal conchse are formed appear at the 

 fifth month. At birth each forms a small triangular lamina in the perichondrium of the ethmo- 

 vomerine plate near its junction with the presphenoid, and partially encloses a small recess from 

 the mucous membrane of the nose, which becomes the sphenoidal sinus. By the third year the 

 bone has surrounded the sinus, forming an osseous capsule, conical in shape, the circular orifice 

 which represents the base becoming the sphenoidal foramen. As the cavity enlarges the 

 medial wall is absorbed, and the medial wall of the sinus is then formed by the pre-sphenoid. 



Fig. 86, — The Sphenoidal Concha at the Sixth Year. 



The bones are subsequently ankylosed in many skulls with the ethmoid, whence they are often 

 regarded as parts of that bone. More frequently they fuse with the pre-sphenoid, and less 

 frequently with the palate bones. After the twelfth year they can rarely be separated from the 

 skull without damage. In many disarticulated skulls they are so broken up that a portion is 

 found on the sphenoid, fragments on the palate bones, and the remainder attached to the 

 ethmoid. Sometimes, even in old skulls, they are represented by a very thin triangular plate 

 on each side of the rostrum of the sphenoid (fig. 87). 



Fig. 87. — The Sphenoidal Concha from an Old Skull. 



Sphenoidal concha 



Rostrum of sphenoid 



THE EPIPTERIC AND WORMIAN BONES 



The epipterics are scale-like bones which occupy the antero-lateral fontanelles- 

 Each epipteric bone is wedged between the squamo-zygomatic portion of the 

 temporal, frontal, great wing of sphenoid, and the parietal, and is present in most 

 skulls between the second and fifteenth year. After that date it may persist as a 

 separate ossicle, or unite with the sphenoid, the frontal, or the squamo-zygomatic. 

 The epipteric bone is pre-formed in membrane, and appears as a series of bony 

 granules in the course of the first year. 



The Wormian or sutural bones [ossa suturarum] are small, irregularly shaped 

 ossicles, often found in the sutures of the cranium, especially those in relation with 

 the parietal bones. They sometimes occur in great numbers; as many as a 

 hundred have been counted in one skull. They are rarely present in the sutures 

 of the face. 



THE TEMPORAL BONE 



'J'he temporal bone [os temporale], situated at the side and the base of the 

 cranium, (contains the organ of hearing and articulates with the lower jaw. It is 

 usually divided into three parts — viz., the squamous portion, forming the anterior 

 and superior part of the bone, thin and exjjanded and prolonged externally into 

 the zygomatic process; the mastoid portion, tlie thick conical posterior part, 

 behind the external aperture of the ear; and a pyramidal projection named the 

 petrous portion, situated in a plane; below and to the medial side of the two parts 

 already mentioned, and forming part of the base of the skull. 



When it is considered in reference toits mode of development, the temporal bone is found 

 to be built up of three parts (figs. 88, 89, 90), which, however, do not altogether correspond to 

 the arbitrary divisions of the adult bone. The three parts are named squamosal, petrosal, 



