1906.] IN MEXICAN LIZARDS. 321 



of the transverse rows often decrease moi'e lapidly towaixls the 

 sides, especially in C. gicttatus. One or two i-ows of granules at 

 the posterior border of the collar are perhaps more frequent in 

 G. guttatus and C. imviutahilis than in C. deppp.i. 



Throat (text-fig. 65 A). — In perhaps the majority of C. immu- 

 tahilis the scales on the centre of the tln-oat are somewhat enlarged 

 so as to form a conspicuous cluster, but there are many in which 

 such a cluster is ill-defined, or absent, regardless of age, sex, 

 and locality. 



Front of humerus protected by scales which vary much in size 

 and in numbers. The size decreases from the anterior or outer 

 margin backwards. Sometimes there are only 3 rows of distinctly 

 enlarged scales, followed by much smaller scales which are con- 

 tinued upon and slightly beyond the back of the elbow ; or there 

 are 4, 5, 6, or even 7 rows of larger scales, and in these latter 

 cases most of the scales are of medium size. Sometimes there is 

 a break, filled by granules, between the anterior larger scales and 

 those on the posterior side above the elbow, which in such cases 

 form a little cluster or nest. Such a nest occurs in Atlantic and 

 in Western specimens. Otherwise the Atlantic specimens seem 

 to be remarkable for possessing only 3 enlarged rows. 



Foste7-ior side of forearm (text-fig. 62 A). — There are no post- 

 antebrachial plates. Almost imiversally, without exception in 

 the Atlantic specimens, the posterior surface from elbow to wrist 

 is covered evenly with small granules. 



Anterior side of forearm. — Mostly with 2|, sometimes with 3, 

 longitudinal rows of transversely broadened plates, very vaiiable 

 in detail. 



Anterior side of femur. — The number of longitudinal rows of 

 scales and plates, between the granules of the dorsal surface and 

 the row of femoral pores, is considerable, about 10 to 12. One 

 row is always distinctly larger than the rest. Including this row, 

 and counting thence to the pores, across the thickest part of the 

 thigh, there are from 7 to 10 rows, mostly 8 or 9. Only in rare 

 cases are all these rows regular ; frequently one or more rows are 

 veiy incomplete, being represented by a few irregularly intercalated 

 scales. The smallest number of rows, wavering about 7 (in one 

 case with even this number imperfect), I have found in the five 

 specimens from and near San Luis ; these specimens are in other 

 respects not at all aberrant, but rather typical C. immutahilis. 

 In an adult male from Agua fria are only 7 rows on the left, and 

 8 very incomplete rows on the right thigh ; in another specimen 

 8 complete right and 9 complete left rows. 



Whilst in C. deppei usually the three biggest row^s, rarely only 

 two, reach down to the knee, in C guttatus -\-im7mdahilis even 

 the biggest row does but rarely extend to the bend of the knee. 



Inner aspect of tibia protected mostly by 3, often by 2g, 

 exceptionally only by 2 rows of large plates. 



The preanal cluster of plates and scales is separated from the 

 ventrals by a rather long and narrow isthmus which is covered 



