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Show 1897.J LIZARDS OF THE GENUS SCELOPORUS. 495 2. S. clarkil differs from S. spinosus in having a greater number of femoral pores (11 to 13 instead of 7 to 10). But as this is the only difference I can perceive, and as I have no doubt an examination of a larger material would reveal greater variation than that with which we are at present acquainted, resulting in an overlapping of the two numbers, I consider this species merely as a form of S. spinosus, which " seems confined to South-eastern Arizona, whence it is found southward into Mexico for an unknown distance, probably confined to the western slope of the Sierra Madre." 3. S. magister and S. fiorldanus (" or S. spinosus fiorldanus if the number of femoral pores should be found to intergrade ") are both distinguished by longer ear-scales, as may be seen from the figures annexed to Stejneger's paper, and the pores number 11 to 16. The character of the auricular scales is, however, much more variable than one would infer on the authority of Stejneger. On comparing his figures with mine (p. 494, d, e,f) and with Bocourt's (pl. xviii. fig. 5), it will be seen that such a character is too inconstant for specific distinction \ in the absence of any others, which I am unable to find and which Stejneger has, so far, not given. I have carefully compared specimens from Texas (S. fiorldanus) with some from Arizona (S. magister), and I a m quite unable to separate them. There is absolute identity between specimens from Waco and from Tampico. I believe geographical considerations have influenced Stejneger in separating the western from the eastern form,-S. magister being found, according to him, in S.W. Utah, the Grand Canon of Colorado, S. Nevada, the desert region of California, and Arizona2; S. fiorldanus from Pensacola to Southern Texas. But I would not allow such considerations to weigh in the distinction of species or even varieties, as they must vitiate any ultimate deductions in the study of geographical distribution. W e know that gaps may occur in the distribution of a species. To mention one example taken from the European fauna, the Eeptiles of which are certainly better known than those of any part of America, I will allude to the common Adder, Vlpera berus, which disappears from the plains of Erance south of the Loire, where it becomes replaced, as well as in the Pyrenees, by V. aspls, and reappears again in the hilly districts of North-western Spain and North Portugal. O n the whole, however, the ear-scales of S. fiorldanus (fig. 2, e) and S. magister (fig. 2, / ) , which I unite as one form, are more elongate tban in S. clarkil and S. spinosus, though they intergrade in Texan specimens (fig. 2, d), and I therefore believe it best to separate S. magister as a variety. The arrangement proposed is the following :- 1. Var. horrldus, Wiegm. Eemoral pores 2-6 on each aide; auricular scales usually not or but slightly longer than broad. 1 In 8. undulatuswe meet with a similar amount of variation, and I am unable to avail myself of the character for defining varieties, in spite of repeated efforts to do so. 2 Has since been recorded from N e w Mexiro. 33* |