16 
THE VOYAGE OF H.M.S. CHALLENGER. 
fig. 347). This skull has a cephalic index of 73'03, and is therefore distinctly dolicho- 
cephalic, its more elongated index being apparently due to its occipital projection. Dr. 
Williamson also, who does not, however, give any measurements, states that the occiput 
is well rounded and frequently prominent in Bush crania. 
The height of thirty-two crania has been given by Barnard Davis, Fritsch, Flower, 
de Quatrefages with Hamy, Rolleston, and myself, and the mean vertical index of these 
specimens is 71, which precisely corresponds with the mean of my six adult crania. 
Seventeen of these crania had a vertical index of either 71 or less, and in one skull 
described by Prof. Rolleston the index was as low as 65 ; in another, from Mr. Oates's 
collection, described by the same anatomist, it reached as high as 78, but this was quite 
exceptional. The Bush crania, therefore, are decidedly tapeinocephalic. It is obviously 
a general character of the Bush skull that the vertical diameter is less than the greatest 
breadth. 
In fifteen crania a gnathic index has been calculated by Flower, Rolleston, and 
myself, from a comparison of the basi-nasal with the basi-alveolar diameters. The mean 
index in these specimens was 97'9, which places the skulls in the orthognathic series. 
Several of the specimens were, however, above 98, which is taken as the upper limit of 
orthognathism, and three reached 102 ; so that individual skulls have a forward 
projection of the upper jaw considerably above the average of the race, but in no instance 
did they attain that degree of prognathism which is characteristic of the negro. The 
want of projection of the upper jaw in these people is also testified to by Dr. "Williamson, 
who in his excellent description of the Bush crania in the Army Medical Museum states 
that "the alveolar processes are straight and broad in front, and do not project, but the 
position of the sockets causes the teeth to stand forwards." 
The nasal index has been computed in twenty-one specimens by Flower, de Quatrefages 
with Hamy, Rolleston, and myse]f, and the mean index is 58'4, which places these skulls 
well into the platyrhine series. The mean of this large series of crania is, however, less 
than that obtained by either Flower, de Quatrefages with Hamy, or Rolleston, in their 
respective series, owing to the low mesorhine indices (48, 49, 50) in three of the specimens 
which I have recorded, and yet these mesorhine crania had in other respects well-marked 
Bush characters. The width of the nasal aperture is also specially referred to by both 
Williamson and Fritsch as a feature in the Bush skull. 
The orbital index has been calculated in the same tw T enty-one specimens, and the 
average is 83, which places the skulls in the microseme series. A considerable range, 
however, prevailed in this index, for in a skull described by Dr. Rolleston it was as high 
as 100, and in another skull measured by the same anatomist it fell to 73. 
The palato-maxillary index has as yet only been recorded in the skulls described 
in this Report; the mean of the measurements of four crania being 119 "5. which places 
these skulls in the brachyuranic series. 
