180 MEMOlES OF THE "NATIONAL ACADEMY OF SCIENCES. 



The vertico-Iongitudinal index was obtained in 40 skulls (Table viii). Its extremes in adult 

 skulls are 78.79 and 97.29. We have a cliild's skull, however, which has an index of but 77.70, 

 and it is well to observe that the maximum index (skull H. 32) is far removed from the rest of the 

 juroup, the next greatest being 9l.\56. The average of 39 adult skulls is 83.24. 



Our lowest index is within the limit of high skulls as given by any known authority. Sir 

 William Turner applies the term acrocephalic to all crania with an index of 77 or above.* 



In the list of the vertico-transverse index (which may be computed in 39 skulls) the lowest is 

 84.82, the highest is 105.88. This belongs to the same skull, which has the highest length-height 

 index, namely, H. 32. In respect to the index now under consideration, H. 32 is not so far 

 removed from the rest of the group as it is in the length-height index, as -R-ill be seen in Table 

 XIV, where the highest five indices are: 105.88, 104.47, 103.G2, 102.27, and 101.39. 



In 36 skulls both the vertico-Iongitudinal and the vertico-transverse indices were ascertained, 

 and from those we were able to determine the mixed index of height of Topinard.t Of these 36 

 skulls the average vertico-Iongitudinal index is 85.40, the average vertico-transverse index 96.49, 

 and the mixed index 90.94. (See Table xvii.) 



A casual glance at the above figures might lead to the conclusion that the pressure on the occip- 

 ital tended more to increase the width than the height of the skull, but such is probably not the 

 case. The transverse measurement is taken wherever the maximum width falls; the height meas- 

 urement iS' taken from ba"Sion to bregma, and the latter is in no case the highest point*on the sagittal 

 suture in this group — it rarely approximates the highest point. If a series of vertical measure- 

 ments were taken from either the German horizontal plane or the alveolo-condylean plane extended, 

 the most distant point of the sagittal suture would usually be foixnd posterior both to the bregma 

 and the vertex of Broca, and often nearer to the obeUon than to either. Thus it probably is that 

 the vertico-transverse index is the greater of the vertical indices. 



§ 12. THE PLANE OF THE FORAMEN MAGNUM OR OPISTHIO-BASILAR PLANE. 



In 29 skulls, where the landmarks were intact, we have determined the degree of inclination 

 of this plane according to the three methods usually employed, i. c, we have taken the aiigle of 

 Daubenton, the occipital angle of Broca, and the basilar angle of Broca. Tables xviii-xxiii give 

 the results of our measurements, recording in no case less than half a degree. 



We are toldf of the angle of Daubenton that its lowest recorded expression is — 16 in an 

 Auvergnean, and its highest + 19 in a Hottentot. In the Hemenway collection we have no minus 

 quantities for this angle ; our lowest is + 4° 30', while our highest far exceeds this exemplary 

 Hottentot, being + 23°. The highest average we have seen mentioned is -f 9.34 in Nubians, but 

 the average of the Saladoans is 13.30. 



The occipital and basilar angles of Broca are, of course, correspondingly exaggerated in our 

 series, the mean and extreme of the former being respectively 24° 15' and 35°, and of the latter 

 32° 15' and 46° ,30' (Tables xx and xxii). The mean of the Nubian basilar angle is 26^ 32'. 



The opisthio-basilar line is very approximately a continuation of the alveolo-basilar line in 

 skulls H. 10 and H. 23, whose angle is, of Daubenton, 18° 30'. A straightedge applied to the 

 median line at the base may be made to almost touch at the same time the alveolar point, the 

 basion, and the opisthion. We may say, then, that the plane of the foramen magnum in these 

 two cases looks directly downward. In skulls H. 18, H. 24, and H. 25, whose angles exceed 18° 30' 

 the plane looks downward and backward. In the rest of the series it looks downward and more or 

 less forward. 



If the inclination of the plane of the foramen magnum were accepted as a measure of evolution, 

 the Saladoans would stand at the bottom of the human scale. We are inclined either to regard 

 their peculiarity in this respect as additional evidence in support of Topinard's opinion that the 



* Turner : The zoology of the voyage of H. M. S. Challenger, P.art xxix, Report on the Human Skeletons— The 

 Crania. Loudon, 1884, p. 5. 

 t Op. cil., p. 683. 

 t Broca: Sur I'augle orbito-occipital, Revue d'Authropologic, t. 6, Paris, 1877, p. 394. 



