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Show 474 MR. G. A. BOULENGER ON THE [May 18, The following papers were read :- 1. A Revision of the Lizards of the Genus Sceloporus. By G. A. BOULENGER, F.R.S. [Eeceived March 29, 1897.] (Plate XXXIH.) The discrimination of species in the genus Sceloporus is beset with great difficulties. Cope has justly recommended it as " an excellent piece de resistance for those persons who do not believe in the doctrine of derivation of species." The discrepancies observable on comparing the revisions published about the same time by Cope1, myself2, and Giinther3 show to what extent opinions may differ on the delimitation of species. I have therefore considered it useful to undertake a renewed study of the genus, embracing the whole material in the British Museum, which has been greatly increased since the publication of tbe second volume of the Catalogue of Lizards, thanks chiefly to the donations of Messrs. Salvin and Godman, Mr. W . Taylor, Dr. A. Duges, Mr. Van Denburgh, and the collections made by Dr. A. C. Buller in Western Mexico and by Profs. Gilbert and Eigenmann in California. I have not restricted m y work to framing diagnoses, but have drawn up tables of measurements and records of numbers of scales and femoral pores4 of nearly all tbe specimens, with the exception of very young ones. These tables, I trust, will prove of more lasting value than systematic conceptions, and be of service to future workers in the same field as well as to those who might wish to test the constancy of the characters on which species have hitherto been established. Coloration, even the most conspicuous markings, I find generally inconstant as a specific character, and liable more often to deceive than to help in identifying specimens if considered previously to the structural characters. Therefore, whilst paying to coloration the attention which it deserves, I have abstained from introducing any allusion to it in the key preceding the descriptions of the species, all of which are based on structural characters. 1 Proc. Amer. Pbilos. Soc. xxii. 1885. 2 Cat. of Lizards, ii. 1885. 5 Biol. C.-Amer., Eept., 1890. 4 These tables read as follows :- 1. Length from snout to vent (in millimetres). 2. Length of shielded part of head (from end of snout to posterior border of interparietal shield). 3. Length of head to ear-opening. 4. Length of tibia. 5. Distance between base of fifth toe and extremity of fourth. 6. Number of scales from occiput to base of tail. 7. Number of scales corresponding to length of shielded part of head. 8. Number of scales round middle of body. 9. Number of femoral pores (right and left). |