406 PEOr. T. JEFFEUr PAEKER ON THE CRANIAL OSTEOLOGY, 



such points as the bregma, lambda, pterion, &c., and as the main object of the measure- 

 ments is to serve as a means of identification, it is important to select standard points 

 which can be readily made use of in any fairly well preserved skull. Moreover, as a 

 matter of convenience it is desirable that the measurements should be made with some 

 common and readily procurable instrument. I have therefore taken them all wdth 

 callipers, so that in the case of curved surfaces, such as the roof of the skull, the chord 

 is given, not the arc. All measurements are given in millimetres ; the standard being 

 so small, fractions are neglected. 



The measurements given are defined as follows : — 



1. Total length of skull: from centre of occipital condyle to anterior extremity of 



premaxilla. 



2. Length of cranio-facial axis : from centre of occipital condyle to tip of rostrum. 



3. Length of basis cranii : from centre of occipital condyle to base of rostrum, i. e. 



to the centre of a line joining the anterior ends of the bases of the basl- 

 pterygoid processes. 



It will be seen that the expression basis cranii is here used in a special sense ; 

 the dimension chosen nearly corresponds with the length of the base of the skull 

 as measured from the condyle to the preoptic ridge. The entire basicranial 

 axis, i. e. from condyle to junction of presphenoid and ethmoid, can only be got 

 at by bisecting the skull, and even then, owing to the ankylosis of the bones 

 named, cannot be determined with precision. 



4. Length of roof of cranium : from the centre of the supraforaminal ridge to the 



middle of a line joining the anterior borders of the lacrymals (preorbital 

 processes). 



Hutton takes the naso-frontal suture as the anterior boundary of this line, but 

 in old skulls the suture is obliterated, and the posterior end of the premaxillary 

 groove which coincides with it is frequently obscure. 

 6, Width of cranium at jiaroccipital processes: the length of a straight line joining 

 the dorsal ends of the paroccipital processes, immediately below the supra- 

 tympanic ridges. Occasionally there is a sort of step where the supratympanic 

 ridge passes into the paroccipital process ; the measurement should then be 

 taken below the step. 



6. Width of cranium at squamosal prominences : length of a straight line joining 



the most projecting portions of the squamosals. 



7. Width of cranium at temporal fossce : length of the longest straight line joining 



the right and left temporal fossae. 



This measurement gives an indication of the width of the brain-case, the walls 

 of the skull being much thinner at the temporal region than elsewhere. 



8. Width of cranium at postorbital pirocesses: length of a straight line joining the 



most prominent parts of the right and left postorbital processes. 



