SNAKES OF THE GENUS PITUOPHIS 49 



paired series of elongated elliptical annuli, a light spot appearing in 

 the center of each annulus. These annuli become progressively 

 shorter and wider posteriorly until slightly posterior to the middle 

 of the body, the pairs fuse in the midline, producing a single series of 

 ovoid annuli posteriorly. Anterior to the vent these lose the light 

 center, and they become black bars on the tail. On the sides there 

 is a series of black spots, which are anteriorly in the form of short 

 bars 3 to 8 scales each in length and 2 to 3 scales in width; posterior 

 to these they appear as smaller rings alternating with the paired 

 annuli of the dorsal series; posterior to the middle of the body they 

 alternate with the dorsal series as small, quadrangular or ovoid spots; 

 and they disappear just posterior to the vent. The total number of 

 spots, paired or single, varies from 26 to 34 on the body (average 

 28.7) and from 11 to 13 on the tail (average 12.2). The ground color 

 in alcoholic specimens is a dirty yellowish white. The under side is 

 yellowish white and lacks spots anteriorly, although posteriorly small 

 black spots appear at the sides of the ventrals and under the tail. 

 These are separated by 2 to 4 scales, and each spot is 1 or 2 scales 

 in length. A few brownish spots are scattered irregularly between 

 these lateral spots on belly and tail. The head is uniformly pale. 

 (Fig. 26.) 



Variation. — Any attempt to correlate the variations in scale counts 

 in this form with its geographical distribution would be futile, since 

 so few specimens are known, and of these only two have definite 

 locality records. 



Sexual variation, however, seems to be apparent in several charac- 

 ters even in this limited series of specimens, of which three are males 

 and only one is a female. The ventrals in males range from 236 to 

 241 and are 249 in the female, while caudals in the female are 61 in 

 number and vary from 65 to 71 in the males. In correlation with 

 the latter character, the tail length is 0.122 of the total length in the 

 female, whUe in the male specimens it varies from 0.133 to 0.137. 

 The female specimen is one of those with the highest number of scale 

 rows, agreeing in this with the similar tendency in other forms of the 

 genus. It has also the lowest number of infralabials, 11, while males 

 have 12 or 13. In correlation with the higher number of ventrals, 

 the female specimen has also a higher number of spots, 45 on body 

 and tail, as opposed to 39 to 40 in males. These variations can be 

 considered significant only as they agree with the general tendencies 

 in sexual variation evident throughout the genus, and furnish con- 

 clusive evidence only if they agree with such information as may be 

 obtained by a later study of a much larger number of specimens of 

 the species. 



Range. — Of the four specimens of lineaticollis examined, only two 

 have definite locality records. These are from Acahuizotla and 



