MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Among the Mound Builders, in a series of 41 skulls there are 6, or over 14i per cent, of which 

 nearly all referred to the incisors. 



The series of Californiaus, 36 in all, exhibit but 4 deformities, or a trifle over 11 per cent. 



Among the Sioux there were found 4 deformities of the dental arch in 34 skulls, or over 1H 

 per cent. 



The Alaskan Indians on the other hand display a much higher percentage of deformity; for 

 out of 41 skulls 8 deformities were found, making nearly 20 per cent. 



TABLE Q. Dental deformity among different American peoples. 



Tuberculation. Prof. Cope* has recently called attention to the absence or slight develop 

 ment of the postero-internal tubercle of the second upper molar in certain races. According to 

 his researches the Eskimos generally have but three tubercles upon the grinding surface of the 

 last two superior molars, representing the tritubercular condition, while the Negroes and Malays 

 display four tubercles upon these teeth, which are, therefore, quadritubercular. These differences 

 are marked and very constant in these races and serve to distinguish two extremes of tubercula 

 tiou. Among the various tribes of American Indians, however, certain intermediate steps are 

 met with, which in the groups considered we have endeavored to represent by percentages. 



Upon the first molar there are always four principal tubercles (two external and two internal) 

 and the grinding face of the crown is always square. In the Negro and Malay the second, and 

 not infrequently the third, molars are similarly constituted; but in the Eskimos the second and 

 third molars bear only three principal tubercles, of which two are external and one internal. The 

 internal cusp is large and crescentic in outline and covers the entire internal aspect of the grinding 

 surface; but it sometimes happens that a faint trace of the fourth cusp is present in the form of 

 a slight ledge or cingulum at the postero-internal angle of the crown. Those skulls in which the 

 second molar has its full complement of tubercles we have marked 4; those in which the tooth 

 displays a trace of the fourth cusp we have marked 3i, while those in which there are only three 

 tubercles we have marked 3. 



Taking the Alaskans as the extreme of the tri-tubercular type we have in 43 examined skulls 

 2!), or over 07 per cent, in which the second molar bears 3 tubercles; 8 of the 43, or over 18 J per 

 cent, display traces of the fourth cusp, and G of the series, or nearly 14 per cent, have the fourth 

 cusp fairly well developed. 



Out of a series of 71 skulls of the ancient Californians 44, or nearly (i2 per cent, are tritu 

 bercular; 15, or about 21 per cent, have traces of the fourth cusp, and 12, or nearly 17 per cent, 

 have all the tubercles developed. 



The series showing the next highest percentage of the tri-tubercular type is that of the Mound- 

 Uuilders, in which out of 37 skulls 15, or 40 per cent, are tri-tubercular; 4, or nearly 11 per cent, 

 have the tubercles 3i, and 18, or over 48.J per cent, have all the tubercles present. 



The condition of the second molar in the Saladoan skulls gives the following results: Out of 

 23 examples 9, or about 30 per cent, are tritubercular, and the remaining 14, or nearly 61 per 

 cent, are more or less quadritubercular. 



Next come the Peruvians, iu whom 19 out of 53 skulls, or about 36 per cent, are tri-tubercular, 

 14 or nearly 26i per cent have the 3.J tubercle, and 20 or over 37 per cent are quadri tubercular. 



Lastly we come to the Sioux, of whose skulls 37 are represented in this series. In these 6 or 



* Journal of Morphology, Boston, 1888, 1889, Vol. n, pp. 7, etc. 



