OSTEOMETRY; THE MEASUREMENT OF THE BONES 73 



substituted for the previous one as the definite measure of the prog- 

 nathism of a skull, it will probably be found advisable to reduce the 

 values of the classes in the classification, to correspond with the re- 

 duction in the size of the angles. GO. 



7. Alveolar profile angle. The inclination of the profile of the alveolar 

 region, measured fromnasospinale to prosthion (its most projecting point) . 

 This angle can be measured only on skulls with complete alveolar region 

 in the median line, and is taken with the stationary goniometer upon an 

 oriented skull, as in the two previous cases. This seems hardly a practical 

 angle to use, although it is generally recommended, since it is too small 

 an angle to take accurately, and since it is too easily affected by varying 

 degrees of projection of the teeth, quite an individual peculiarity and not 

 racial. GO. 



8. Profile angle of ihz nasal roof (the nasal bones). Inclination of the 

 nasion-rhinion line, measured in the same way as the last, the two points 

 of the goniometer resting upon the termini of the line in question. To be 

 used only in skulls in which the nasal bones are complete. GO. 



9. Calvarial base angle. The inclination of the nasion-inion line ( = 

 calvarial base) to the FH. This is readily measured with the stationary 

 goniometer on a skull placed upon the FH in a cubic craniophore. The 

 craniophore is placed so that the norma occipitalis is beneath, and the 

 norma verticalis towards the instrument. The two points rest respec- 

 tively upon nasion and inion, and the angle shown is the complement 

 of the one sought. 



The knowledge of the usual values of this angle and of Schwalbe's 

 frontal angle (2) will allow one to place a fragmentary cranium upon 

 approximately its proper position, and save one from making such erro- 

 neous conclusions concerning the set of the head and the slope of the 

 forehead in life, as was most unfortunately done in the case of the sup- 

 posed Diprothomo platensis of Ameghino. Fragmentary skulls, consist- 

 ing of calvarium alone, and this often badly broken, are so frequently 

 found that a knowledge of this angle, giving the usual relationship of the 

 nasion-inion line, is extremely useful.* 



10. Inclination of the occipital foramen. This is naturally the inclina- 

 tion which the plane placed across the foramen, and including both basion 

 and opisthion, makes with the plane of the FH, i.e., a dihedral angle, but 

 in a symmetrical skull it should have the same value as the angle made 



* For the studies of G. SCHWALBE concerning the proper orientation of a skull 

 fragment, based upon the usual relations of the nasion-inion and glabella-lambda 

 lines, cf. Zeitschrift fur Morphol und Anthropol. Sonderheft, 1906. Das Schadel- 

 fragment von Brtix, and especially the diagram on p. 137, where the usual angle 

 lambda-glabella-inion is given as 20, and the angle glabella-inion FH as 15. The 

 author, like the rest of the world, was then using the glabella, instead of the nasion 

 for all such data (e.g., the calvarial base), as is here the case. For the critical study 

 of Diprothomo by the same author cf. Zeitschr. fur Morphol. und Anthropol., Bd. 

 XIII, 1910-1911, pp. 209-258. 



