NO. 2179. VARIATION IN GARTER SNAKES— THOMPSON. 353 



Variation in Postoculars. 



In this scries the variation in the postocular shields is limited, much 

 more so than in the Sausalito specimens. When the number is 

 reduced to two it is due to the fusing of the normal middle and inferior 

 shields ; when increased to four it is due to the dividing of the inferior 

 shield. In the specimens showing variation in this character 50 per 

 cent are males. 



Per cent. 



3 normal 96 



3-2 asymmetrical 2 



3-1 asymmetrical 2 



Variation in Anterior Temporal. 



This shield is subject to but slight variation. When there are two 

 it is due to a separation of the antero-external angle of the parietal. 

 This part of the parietal is at times dented or partially incised. The 

 single specimen showing an aberration in this character was a male. 



Per cent. 



1 normal 98 



1-2 asymmetrical 2 



Variation in Posterior Temporals. 



These shields exhibit considerable irregularity as to shape and size. 

 Their number may be increased to three; very rarely they become 

 fused into one. The abnormal specimens were all females. 



Per cent. 



2 normal 92 



2-3 asymmetrical 4 



3 bilateral 4 



Variation in Supralabials. 



The normal is 8 supralabials with the fourth and fifth bordering the 

 orbit. When the number is reduced to 7 it is due to the fusing of the 

 normal second and third shields (66 per cent), or the sixth and seventh 

 shields (33 per cent). None of the specimens in this set showed the 

 increase to 9 supralabials which is known to occur at times in this 

 species. In the specimens showing variation in this character 20 per 

 cent are males. 



Per cent. 



8 normal 90 



8-7 asymmetrical 10 



Variation in Infralabials. 



The normal count is 10 infralabials. When the number is de- 

 creased to 9 it is due to the fusing of the normal thii'd and fourth 

 shields (82 per cent), or the normal seventh and eighth (18 per cent). 

 When the number is further reduced to 8 it is due to the fusing of 

 these same pairs — namely, the third and fourth and the seventh and 



G500S°—Proc.N.M. vol.52— 17 23 



