| | | | | Alveolar | | | | | length, | 2.7 | 2.9 | 2.9 | 3.0 | 3.0 upper molars | (2.5-2.8) | (2.9-3.0) | (2.8-3.1) | (2.9-3.2) | (3.0-3.1) | | | | | | | | | | Postpalatal | 4.8 | 5.9 | 6.2 | 6.5 | 6.5 length | (4.5-5.3) | (5.8-6.0) | (5.8-6.6) | (6.2-7.2) | (6.3-6.7) | | | | | | | | | | Breadth | 8.1 | 8.5 | 8.4 | 8.6 | 8.6 of braincase | (7.8-8.7) | (8.5) | (8.0-8.7) | (8.3-8.9) |(8.4-8.8) -------------+-----------+-----------+-----------+-----------+----------- SECONDARY SEXUAL VARIATION The method employed by Dice and Leraas (1936:2) was used to measure the secondary sexual differences, if there were any, in each of several age classes. As pointed out by Hooper (1952b:11), individual variation in small samples can obscure secondary sexual differences. The samples of _B. taylori_ from the vicinity (see page 595) of Altamira, Tamaulipas, and the samples of _B. musculus_ from El Salvador (table 2) were large enough to prevent individual variation from obscuring sexual differences. Nevertheless, no significant secondary sexual differences were found in either _B. taylori_ or _B. musculus_ (see table 2). Therefore, the sexes have been considered together for purposes of geographic studies. TABLE 2.--Analysis of Secondary Sexual Variation in Adult B. taylori Vicinity of (see p. 595) Altamira, Tamaulipas, and Adult B. musculus from El Salvador (see p. 595). (One Standard Deviation on Either Side of the Mean is Given.)