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Show 310 DR. II. GADOW ON EVOLUTION [Mar. 20, thumb procedure, applied to 86 specimens, gives the following result:- Number of femoral rows Southern Oaxaca Tierra Colorada Rio Balsas i CL V c 6 4 . to 5 2 2 5 3 10 1 14 6 10 8 17 11 46 6-7 1 1 2 1 5 7 2 2 14 18 8 1 1 Mean number of rows. 6-0 5-4 6-0 65 specimens. This tabulation is naturally very imperfect, not to say crude, but the results will not be altered when we throw the intermediate or doubtful cases of 6 to 7 rows either into the column with 6 or into that with 7 complete rows. There wrere, for instance, amongst the Oaxaca specimens four with 5 or 6 row7s, but amongst those of Guerrero only two such doubtful cases. The fact remains, that, if we take Tierra Colorada as normal, those further south tend to possess fewer femoral scales, whilst those further north, at Rio Balsas, have decidedly more scales. This does not seem to be the result of mere chance, because, as we shall see, the Balsas specimens are remarkable for other features, although they are not peculiar to them. Amongst the specimens from the State of Oaxaca no difference whatever can be discerned with reference to their habitat nearer to or further away from the coast. At any rate the amplitude is considerable, the extremes being two specimens with an imperfect 5th row, and one with 8 rows; the latter specimen, from Tequesixtlan, is in every other respect a typical C. deppei. Inner side of tibia protected by 2, 2 j, or 3 complete rows of enlarged scutes. Preanal region.-As a rule there are 3 large scales which form a triangle, with two at the base and a third of equal size on the top, but sometimes a fourth scale forms the apex; or the two basal scales are small, whilst the third is correspondingly enlarged. In the majority the whole cluster is separated from the ventrals by a very short isthmus, sometimes so short that the cluster and the ventrals almost touch each other. The isthmus itself is mostly covered with very small scales, and when these are larger they are fewer in numbers. The whole character is worthless. Femoral yores.-The number of pores frequently differs on the right and left side by one, rarely by two, in the same individual. There is no preference for one side. The smaller number in these cases of asymmetry is always due to one or more pores remaining undeveloped at the proximal, or more frequently at the distal end of the series. For comparison, the higher number should therefore always be taken. The amplitude of individual variation is considerable, when we recollect that these pores correspond in numbers with transverse rows of scales. But unfortunately the |