1905.] OSTEOLOPrY OF THE MASTIGUKE LIZARD. 7 



That half of the supposed S!;]uamosal which is applied to the 

 parietal rests upon a thin splinter of bone which is, I think, but 

 am not quite certain, continuous beneath with the cut-ofi' portion 

 of the supposed squamosal. The latter therefore evidently consists 

 of two quite separate parts, which are not distinguished in 

 Gegenbaur's figure already referred to. The question is, what are 

 these two bones ? but, before attempting to answer it, we will 

 consider the same region of the skull of Iguana which is figured 

 (not very satisfactorily) in Bronn's ' Thierreichs' *. In that lizard 

 (see text-fig. 4, B, p. 8) a rounded bone lies between the parietal, 

 occipital, quadrate, and reputed squamosal. This bone may be 

 the segmented- oft' portion of the squamosal complex in Uromastix, 

 or it may be the tiny bone in the same lizard which lies (see 

 text-fig. 4, C) closer to the occipital, and which must be a 

 supratemporal. If we compare the arrangement of the bones 

 in the squamosal region of Uromastix with that in Lacerta as 

 figured by Parker f, it would seem that we have, as in that lizard, 

 two supratemporal bones of unequal size : the smaller of these is 

 that wedged in close to the occij)ital ; the larger is the external bone 

 overlapping the real squamosal and commonly termed squamosal. 

 Parker observes + that " in many kinds (of lizards) .... the first 

 supratemporal is wanting, the second is constant." If by the 

 latter half of this statement the constant presence of a sepa- 

 rate second supratempoial is meant, I venture to disagree with 

 Parker. It does, howevei-, apparently exist commonly, and is 

 figured, for example, in Gerrhonotus by Siebenrock §. I use the 

 word "apparently" advisedly; for I am not yet convinced that 

 the bone in qu.estion is not in reality, as I have already suggested, 

 the squamosal. 



I may point out that the way in which I have ventured to 

 interpret the bones of the region of the skull is quite in accord 

 with Shufeldt's description of the skull of Heloderma ||. Iir this 

 lizard, Shufeldt describes as squamosal the bone which I have so 

 named in Uromastix spinipes, and describes as a " fragment of 

 the hinder end of the zygomatic arch " a rudiment which un- 

 doubtedly corresponds with the squamosal multorum auctoruin. 

 I detect in a specimen of Heloderma forming part of the collection 

 in the Society's prosectorium (text-fig. 4, D, p. 8) a bony nodule 

 lying between the occipital and the squamosal, which I identify with 

 the second supratemporal of Lacerta and of Uromastix spmipes. 

 Siebenrock % has come to the same conclusion with regard to the 

 bone that is in my opinion to be regai'ded as the true squamosal. 

 But he terms that bone which I venture hei'e to call supia- 

 temporal, " Paraquadratum." He does not appear to have seen 



* Vol. vi. Reptilieii, Taf. 68. f. 7. 

 t Phil. Trans. 1879, pi. 42. fig. iv. 



I Loc. cit. p. 599. 



§ "Zur Keiiutniss d. Kopfskelet. d. Sciucoiduii," Ann. k.-k. Hofinus. Wieii, vii. 

 pi. xii. tig. 8. 



II " Contributions to the Study of Heloderma susperftnii,''' 1'. Z. S. 1890, p. 11-8. 

 ^ " Das Skelet der Agamidte," SB. k. AkaJ. Wiss. Wien, civ. p. 1112. 



