A Method of Craniometry for Mammals. 49 



Indices. 



In order that the measurements of any two or more 



skulls may be satisfactorily compared, it is necessary to 



employ indices. From the data obtained, as indicated in the 



preceding paragraphs, indices maybe computed as follows : — 



^ ... ^ , Breadth of cranium X 100 



tephaiic Index = = ~r — ? * 



'^ Length oi cranium 



^„, ^,. -. , r , Oblique height of cranium X 100 



Oblique Altitudmal Index = — ^^ -. — -r. : 



^ Length oi cranium 



,^ .-,,,. ,. TTi Vertical height of cranium X 100 



Vertical Altitudinai Index = ^ —. — . 



Length ot cranium 



^, , . y. , Bistephanic diameter x 100 



tbtephanic Index = ^= r-:, ^ • 



Irontal length 



„ . 1 T ^ Breadth of face x 100 



racial index = =— = -^r^ • 



Length ot lace 



„ , . ^ , Breadth of palate X 100 



Falattne Index = —^ — r • 



Length ot palate 



^ . . . - ^ . Fronto-parietal length x 100 

 Upper Craniofacial Index = ^ — — t-J- ' 



^ . r ' 1 T 1 Lensfth of face x 100 



Lower Cranio-faciat Index = -— ■. — - — r—r\ ^ • 



Cranio-laciai length 



The cephalic index shows the breadth of the posterior part 

 of the skull in relation to the length of the cranium ; but 

 does not indicate the relation between the breadth of the 

 cranial cavity and the cranial length; the outward curve of 

 the zygomatic arch varying very much in different species. 



A comparison of the oblique and vertical altitudinai i'tidices 

 serves to bring out the amount of slope of the roof of the 

 cranium and the degree of vertical development of the 

 occipital region. 



The Stephanie index will be found to indicate the extent 

 of the temporal fossa, and, generally speaking, varies in 

 inverse ratio to the development of the Temporalis muscle. 



Anthropologists, in stating the facial index, take the 

 breadth of the face as equal to 100 • but, seeing that the 

 face of mammals is generally longer than it is broad, it is 

 better to take the length as 100 and compare the breadth 

 with it. The same departure from anthropological methods 

 appears to be necessary in computing the palatine index; 

 and for the same reasom 



VOL. XV. D 



