639 



epiptericmn tj|>i('um can sliow just (he same condition as a siiiill 

 ■with a unilateral processus frontalis of the tirst type. 



Tiiat in case of a unilateral os epiplericuni typicuni the right 

 side is predominant to the left one is due to the predominance of 

 the fi'ontal process of the first type on the left side. 



If at the side of the skull, opposite to an os epiptericura typicum 

 a spheno-parietal suture is found, then the same I'ules hold for the 

 sitnation of this suture as by a unilateral frontal process; that part 

 of the skull that lies symmetrical to the pteric bone can be included 

 as well in the alisphenoid as in the frontal or parietal bone. 



II. I found an os epiptericum of the second type in 7 skulls; in 

 one on both sides and symmetrical, in 5 on the right and in one 

 on the left side. This pteric bone was always combined with a 

 frontal process of the tirst type. For the composition of the pteric 

 region of the opposite side of the skull in a unilateral occurrence 

 of such a pteric bone can be referred to the description of the 

 frontal process. 



III. An OS epiptericum of this type I found only once in a skull 

 as a little sutural bone in a fronto-teraporal suture. 



IV. Several ossa epipterica I observed in '4 skulls; always two 

 bone-pieces were present. In 3 skulls they were on the right ; in one 

 on the left side. 



For the behaviour of the side of the skulls opposite to those 

 with two pteric bones, I refer to the descriptions before mentioned. 



All in all I found pteric bones in 42 skulls, or 36.8 "/o Hi'^t is 

 to say in 5 on both sides, in 23 on the right and in 14 skulls 

 on the left side. 



This enumeration proves that pteric bones are more often found 

 on the right than on the left side, on the contrary the fusion of 

 the bone pieces in the pteric region with one of the surrounding- 

 bones, specially the squamosal, happens more frequently on the left 

 than on the right side. 



It is impossible to decide by this study the meaning of the 

 pteric bones. 



The frequent occurrence of these separate bone-pieces in papuan- 

 skulls is not favourable for Ranke's theory, saying they ought to 

 be considered pathological. 



Ontogenetical and comparative anatomical researches will be 

 necessary to explain this question of the anatomy of human skull. 



41* 



