SNAKES OF THE GENUS PITUOPHIS 91 



more readily derivable from that of affinis than from that of deppei 

 both in the size and shape of the spots and the coloration, although 

 in deppei as in vertebralis we find the orange interspaces between the 

 spots, which are lacking in affinis. In most of the scale characters, 

 as for example the dorsal scale formula, number of ventrals, supra- 

 labials, and infralabials, affinis is intermediate between deppei and 

 vertebralis. It will be noted that vertebralis resembles the more 

 southern specimens of affinis, rather than the more northern, in scale 

 characters, and doubtless arose from the southern group of affinis. 

 The number of scale rows, ventrals, and supralabials decreases in 

 vertebralis from south to north, or away from the southern part of the 

 range of affinis. This would be expected if vertebralis were derived 

 from the latter form, as a result of the separation of the two forms by 

 the invasion of the present Gulf of California. 



The derivation of vertebralis from annedens seems highly improb- 

 ble in consideration of the much greater number and smaller size of 

 the dorsal spots in the latter, as well as their vastly different shape. 



The probable affinities of vertebralis and the neighboring forms may 

 be expressed in the following diagram: 



catenifer^ 



\ 



^deserticola 



/ 



annectens'' 



vertebralis^ 



affinis 

 (northern) 



\ \ 



^affinis 

 (southern) 



1 



deppei 

 Table 9 lists the specimens of this form that have been examined. 



PITUOPHIS SAYI SAYI (Schlcgel) 



Coluber sayi Schlegel, Essai sur la physionomie des serpens, p. 157, 1837 (type 

 unknown; type locality, Missouri). 



Coluber melanoleucus var. Say Harlan, Journ. Acad. Nat. Sci. Philadelphia, vol. 

 5, pt. 2, p. 360, 1827; Medical and physical researches, p. 123, 1835. 



Pityophis sayi Baird, U. S. and Pac. R. R. Explor. and Surv., vol. 10, pt. 4, No. 4, 

 pi. 29, fig. 45, 1859.— Hatden, Trans. Amer. Phil. Soc, vol. 12, p. 177, 

 1863.— Hoy, Geol. Surv. Wisconsin, vol. 1, p. 424, 1883.— Hurter, A 

 catalogue of the reptiles and batrachians collected in the State of Missouri, 

 p. 4, 1883.— Cope, Proc. U. S. Nat. Mus., vol. 11, p. 398, 1888.— Johnson, 

 Trans. Wisconsin Acad. Sci. Arts Lett., vol. 13, p. 527, 1901. — Strecker, 

 Trans. Texas Acad. Sci. for 1901, p. 97, 1902. — HuRTERand Strecker, Trans. 

 Acad. Sci. St. Louis, vol. 18, No. 2, p. 25, 1909. — Strecker, Baylor Univ. 

 Bull., vol. 13, Nos. 4 and 5, p. 15, 1910. 

 136423—40 7 



