74 BULLETIN 17 5, UNITED STATES NATIONAL MUSEUM 



apparently advanced farther than melanoleucus. It must be con- 

 cluded, therefore, that both melanoleucus and mugitus have been 

 derived du-ectly, but independently, from ruthveni, wliile lodingi is a 

 later and more highly specialized derivative of the same form, and is 

 intermediate only in geographic position between ruthveni on the one 

 hand, and melanoleucus and mugitus on the other. 



The probable relationships of mugitus and the neighboring forms 

 have been expressed by the diagram on page 63. 



Table 6 lists the specimens of mugitus that have been examined. 



PITUOPmS MELANOLEUCUS KUTHVE^a Stull 



Pituophis melanoleucus ruthveni Stull, Occ. Pap. Mus. Zool. Univ. Michigan, 

 No. 205, p. 1, 1929 (type, U. S. N. M. No. 76278; type locality, Longleaf, 

 Rapides Parish, La.); No. 250, p. 3, 1932. — Burt, Journ. Washington Acad. 

 Sci., vol. 25, No. 8, pp. 381-383, 1935 (part). 



Original description. — The following description of the type has 

 been given by the writer (Stull, 1929, p. 1): 



The scales are keeled, with the exception of the seven outer rows of either side. 

 The squamation is as follows: scale rows 31-33-25; ventrals 219; caudals 59; 

 supralabials 9/8, the fifth entering the eye on the right side, the fourth on the 

 left; iufralabials 15; preoculars 1, postoculars 4; loreal present; rostral twice as 

 long as wide, penetrating two thirds of the distance between the internasals; 

 frontal undivided. 



The dentition is as follows: mandibular teeth 18; maxillary teeth 15; palatines 9; 

 pterygoids 8. 



The ground color of the dorsum is pale brown, becoming progressively paler to 

 white posteriorly. A mid-dorsal series of dark chocolate brown spots numbering 

 41 on the body and 9 on the tail is present; the spots are largest in the midregion 

 of the body. Additional smaller dark brown spots are present on the sides of 

 the body, forming two rather indefinite alternating rows on either side of the 

 mid-dorsal series on the anterior part of the body. These smaller spots fuse to 

 form one lateral series on either side posteriorly and fuse with the mid-dorsal 

 spots just anterior to and on the tail. The belly is white with a series of rec- 

 tangular dark brown spots at either end of the ventral scutes, and numerous 

 additional spots scattered irregularly between. The spots of the lateral series 

 are one to two scutes in width and are separated by two to five scutes. The 

 under side of the tail is irregularly spotted with brown. [Fig. 41.] 



Total length 1,520 mm.; tail length 200 mm.; tail length 12.5 percent of the 

 total length. 



Diagnosis. — This form is to be distinguished from all other sub- 

 species of Pituophis melanoleucus by its coloration and the larger 

 number of dorsal spots. Thus m. melanoleucus is white, with 30 to 37 

 black spots on the body and tail; m. mugitus is pied rusty brown and 

 white; the dorsum of the anterior part of the body is almost uni- 

 formly brown with the spots indistinguishable in most specimens; 

 the spots of the posterior half become decidedly red approaching and 

 on the tail; and the spots, when distinguishable, do not exceed 39; 

 m. lodingi is uniformly black above and slate-gray below; while 



