OCR Text |
Show 1906.] IN MEXICAN LIZARDS. 307 The principle here involved is to a certain extent expressed by the homely saying, " what is one man's meat is another man's poison." It may be expressed by the following equations:-If x and y are two lizards in an indifferent state, or before they have been subjected to very different modifying oecological conditions, A standing for Plain, B for Forest, and U the result, then xA = B and yB=B, i. e. xA can only be =yB if x and y are different, i. e. reacting differently; it being also inconceivable that the same kind of creature, if modified at all by the absolutely different factors A and B, should be modified into the same combination of characters. xA = yB. x= ^-i i.e. x = 2nd species as it would be if adapted for A Forest life, but modified by the Plain. _ _:> i.e. y = 1st species as it would be if adapted for B Plains, if it were not modified by Forest life. Let us, for argument sake, assume that Plains favour the development of scutes on the forearm, 4 supraoculars and few pores; and that Forest life increases the number of pores, while it disallows or destroys scutes. Then our equation would mean : x = a Forest species which has been changed into one for Plain life; i. e., it has developed arm-scutes, retains all the supraoculars but requires few pores. y = a Plain species which has been adapted to, or changed by, Forest life; i.e., scutes are reduced and pores are increased. In other words, x and y, the original stocks of C. sexlineatus and C. deppei, must have been different. On the other hand, to assume x=y would imply that A=B; physical conditions which we started with as being opposite to each other. CNEMIDOPHORUS HYPERYTHRUS Cope. Cope, Proc. Am. Phil. Soc. 1869, p. 159, established the genus Verticaria for those Cnemidophorus-like species which are distinguished by the fusion of the two frontoparietal plates into one. Such species are C. heterolepis Tschudi, from the neighbourhood of Lima, Peru, and C. hyperythrus Cope, from Lower California, in which I include, following Boulenger's advice, C. sericea van Den-burgh and C. beldingi. Hedracantha Bocourt is, as Boulenger has shown, not a Cnemidophorus but an Ameiva, and does not occur in Mexico as stated erroneously by Bocourt and Cope, but near the coast of Peru and Ecuador. The fact that the fusion of the originally double frontoparietals occurs in two different genera, and the unique scaling of C. heterolepis, appear sufficient to disallow the fusion as a generic character. I a m inclined to look upon these few " Verticarias " as remnants of a more Western, Pacific fauna, and in m y paper Proc. R. S. 1905, I have given reasons which indicate a former westward extension of Mexico and Central America. PROC. ZOOL. Soc-19C6, VOL. I. No. XXI. 21 |