334 BR. H. GADOW ON EVOLUTION [Mar. 20, 



other, and differ in the average from the typical, Northern, 

 G. gularis gulm^is by their larger forearm-scutes, small number of 

 rows of scales on the humerus and femur, the small number of 

 pores, the pink throat and decidedly strong and uniform black 

 pigmentation of the chest and abdomen, and lastly the tendency 

 to develop a 4th pair of pale stripes in the mid-field besides the 

 usual 3 paii's. I thei'efore distinguish this small race as G. gularis, 

 var. meeki. In favour of its claim to distinction is the fact that 

 this combination of characters does not occur elsewhere but in 

 North-eastern Mexico. 



Onemidophorus SEMiFAseiATUs Copo. 



Based by Cope upon three specimens, one from San Diego, 

 Texas, and two from near Patos in the State of Coahuila, west of 

 Monterey. 



Cope gives the following definition : No light stripes ; oliva- 

 ceous with three rows of black spots on each side on anterior 

 fourth of body ; femoral s 8 (but 6 in the text and in the figure !) ; 

 limbs unspotted ; medium size. 



To judge from his description and the figure in the text, the 

 collar is but feebly developed, although the scales are larger than 

 in the tessellatus-gvon^. Humeral scales in 6 rows. Postante- 

 brachials with enlarged polygones in 3 or 4 rows, all distinctly 

 small in the figure. Femoral pores 20. Length 100 mm. 



The colour of all the under parts is uniform olivaceous, without 

 any spots. The upper parts are uniform olivaceous with the 

 following black marks : three rows of black spots on each side ; 

 the superior small, subquadrate ; the second larger and trans- 

 verse, the inferior forming short cross-bars. The lower row is 

 the longest ; the upjoer is the shortest, extending only to the 

 middle of the trunk. 



These two specimens from Coahuila are interesting as showing 

 that a race of Lizards belong to the gidaris-gYO\x^ has reached the 

 light-coloured monochrome stage with black marks or spots, 

 which, being the remainder of the originally dark fields, are 

 themselves reduced from behind forwards. This race therefore 

 forms an analogon to the var. ritbida of the tessellatus-growp 

 (text-fig. 70). 



If, as Cope himself suggested, the solitary specimen from San 

 Diego, Texas, described by him as G. gularis sericetos, is the female 

 of semifasciatus, we can follow the coloration of the latter a 

 stage further back. The specimen measures only 81 mm. Throat, 

 limbs, and tail " yellow," with a bluish patch across the throat ; 

 chest and belly bluish olivaceous. Ground-colour above anteriorly 

 black, posteriorly olive. With 7 paler stripes which fade away 

 towards the rump. The fields are black, with olive spots 

 anteriorly, which enlarge farther back, breaking up the fields. 

 Pores 21. 



It may be accidental, but in all these three specimens the 

 4th supraoculars ai-e broken up each into two smaller scutes : 



