SNAKES OF THE GENUS PITUOPHIS 



9 



collis only the posterior part of the dorsum bears the typical median 

 series, while the midregion bears two series of amiuli, and the anterior 

 part of the body is distinguished by the presence of two continuous 

 black stripes. In the four subspecies of melanoleucus the typical pattern 

 is variously modified by intensification or diminution of color in the 

 background or spots, or by the fusion of spots, rendering the anterior 

 background dark with the spots only slightly darker in ruthveni, the 

 anterior spots so blended with the background as to be indistinguish- 

 able in mugitus, and the dorsum uniformly black in lodingi. The 



FlOUBE 4. — Head of Pituophis catenifer deserticola: a, From the side; 6, from above. 



number of spots, when distinguishable, varies within a wide range in 

 the different forms, from 21 to 94 on the body, and from 5 to 36 on the 

 tail. The coloration of the belly varies from an immaculate white to 

 white heavily spotted with black throughout. 



Range. — The range of this form extends from Guatemala to Canada 

 and includes most of Mexico and all the United States west of the 

 Mississippi, and, east of the Mississippi, Wisconsin, Illinois, Indiana, 

 Tennessee (?), and all the States of the Atlantic coast from Alabama 

 to southeastern New York. 



Habits and habitat. — Of most of the forms of this genus, as indeed 

 of most reptiles, little or nothing is known of the habits or habitat. 



