PREHISTORIC TIMES IN BRITAIN. 535 



classification or identification of other animals, or in that furnished 

 by the facts of its own developmental history. 



The nasal and the frontal bones together form a roof over the 

 ethmoid and the turbinal bones ; and as there is no apparent phy- 

 siological reason why they should contribute in different propor- 

 tions towards the securing of this end, the fact that they do so is 

 of so much the greater morphological value. In Sus cristatus the 

 naso-frontal suture very ordinarily runs (also in Sus andamanensis) 

 straight across the roof of the ethmoid, at right angles to the long 

 axis of the skull ; or the frontals may intrude themselves mesially 

 between the nasals, making thus the contour of the suture to be 

 convex forwards. Precisely the reverse is the case in the adult 

 European wild boar. Some weight has been laid ^ upon a similar 

 conformation in the skull of the tiger, as being of service in difier- 

 entiating it from the skull of the lion ; and though it is not 

 pretended that an equally great distinctness can be supposed to 

 exist between the two animals now under comparison, still the 

 structural differences in the two sets of cases are analogous. 



But when we come to look at the skulls of developing pigs, we 

 see that real value attaches, from this point of view also, to the 

 relatively greater or less extension backwards of the nasal bones, 

 and the contour described consequently by the naso-frontal suture. 

 A tape crossed at right angles to the long axis of the skull from 

 one infra-orbital foramen to the other, passes very closely in front 

 of, and often parallel with the naso-frontal suture in the very 

 young pig ; the suture gets removed further and further away 

 from it as the pig increases in age. Nathusius (Taf. iii. figs, ii 

 and 13) has figured the skulls of a young wild boar and of an adult 

 wild boar upon the same plate ; and the straight line of the suture 

 of the former contrasts most instructively with the backwardly 

 arching contour of the latter. The straightness, therefore, of the 

 naso-frontal suture may be supposed to illustrate the principle 

 that climatic or other conditions may cause structural arrange- 

 ments to be permanently retained in certain races whilst they are 

 obliterated in others. The retention of the prolongation of the 

 sagittal suture over the frontal region is believed, with much 

 reason, to be hereditarily transmitted in our own species ; and I 

 incline to think that the persistence of the frontal tubera with 

 ^ ' Ost. Catalog. Royal College of Surgeons of England,' 4506, p. 706. 



