MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 183 



each and every series, it is, of course, the type skull of the lot in every respect, so far as the 

 investigation has gone. 



Hut if, as must always be the case, no skull expresses the theoretical mean of every series of 

 indices, then we take the skull which averages nearest the theoretical mean. Therefore, of our^ 

 supposed lot of 9 skulls we select, let us say, from the first series of indices, 3 the .skull 

 having an index most nearly expressing the mean of variation, the skull having an index next 

 greater than this, and the skull having an index next smaller. Now, supposing that we have ten 

 series of indices, let us say that the skull which expresses the theoretical mean of the first series 

 comes nowhere near it in any other series, while the skull next below the theoretical mean iu the 

 series of indices under consideration is the theoretical mean of two other series of indices, and 

 stands either just above or just below the mean in every series. The latter, then, is very likely 

 the type sought. 



To state it more methodically : We have measured a lot of skulls, have reckoned their indices, 

 and have arranged the several different kinds of indices in as many different ordinations, hi each 

 ordination we select the index most nearly expressing the mean of variation and call it No. 1 ; the 

 index next above and index next below this we call No. 2. The index next above the greater No. 

 2, and the index next below the, lesser No. 2 we call No. 3, and so on. Now let us add together, 

 for each skull separately, the Nos. 1, 2, 3, etc., expressing the position of the several indices with 

 regard to t he theoretical mean of radiation of each series of indices. Divide the sum thus obtained 

 by the number of series of indices. The skull whose indices thus treated give the lowest quotient 

 is the type. 



In the. present case, however, it must be remembered that theSalado skulls are much broken, 

 so that only a few can yield a complete series of measurements. The type skull, therefore, in part 

 owes its selection to its good preservation, it being represented in every series of indices. It can 

 not be said to be the type of 57 skulls, perhaps, but in a general way, all things considered, 

 it is the best representative of the characteristic dimensional relations of crania of the people 

 in question. Its most aberrant feature consists in the uuusal height of the orbits, shown by the 

 orbital index 90.05, while the theoretical mean of the orbital indices is 1)0.90. 



The type skull thus selected is II. 40; its five views are shown in plates 55 to 50, inclusive. 

 Of skulls in good condition H. 7 and H. 15 approach nearest to the type. 



$ 15. PROCESSES AT 15ASE OF SKULL. 



There is evidence, in the arclueologic find of Los Muertos and Las Acequias in the shapes of 

 the pottery, etc., that this people, like the modern Pueblos, were accustomed to carry heavy 

 burdens on the head. Such being the case, we might reasonably expect to find the various proc 

 esses for muscular and ligamentary attachments at the base of the skull strong and prominent; 

 but, on the contrary, we find them unusually subdued and weak. It may be that our expecta 

 tions are, unfounded; that the load on the head, oiice well balanced, required little muscular exer 

 tion to sustain it. 



The fnion. In 4(i adult skulls, with this process well preserved, compared with the live 

 forms of Broca,* we find that 27 agree with his zero or lowest form, that lit resemble his No. 1, 

 and that none arc to be considered of a higher grade than this. It has been conjectured that the 

 general pressure which has flattened the occiput in these skulls may have hindered the full 

 development of the inion; but the fact that all the processes of the base arc weak, and that the 

 inion is ill-developed in skulls where the pressure did not fall upon it, seems to indicate that pres 

 sure can at most account for only a part of the subdued features of the inion in this series. 



$ 16. THE PTERION. 



Of the pteria 32 are sufficiently preserved to be studied with profit. They occur in 24 skulls, 

 13 on the right side, 19 on the left. Four exhibit the character plainly, but can not be measured. 

 The remaining 2S (see Table xxv) are easily measured. Only 8 skulls have the pteria intact on 

 both sides. 



Instructions cruuiulogicniuH ct crnuiomctriiiuc*. I l. vi. 



