164 BULLETIN 61;, UNITED STATES NATIONAL MUSEUM. 



The latter three specimens have been referred by Cope to sumi- 

 cJirasti, and conform closely to the original description of that form. 

 Inasmuch, however, as it is impossible to work out the dorsal scale 

 formula of the type (owing to its poor condition) the identity of the 

 Zacaultipan specimens with them can not now be determined. The 

 species was described, however, from specimens from Orizaba, Mexico, 

 and credited with 19 scale rows, which probably means the maximum 

 number, and since specimens from that locality have generally a 

 more reduced number of dorsal scale rows (although the maximum 

 is frequently 19) and a similar coloration, the types of sumichrasti 

 are undoubtedly identical with such specimens which are to be 

 referred to a different form. I believe the specimens from Zacaulti- 

 pan, without stripes, can be considered only as variations of eques, 

 which possibly indicate that the form tends to lose the stripes in this 

 region." 



Affinities. — If I have proven that there is a tendency toward a 

 reduction in the dorsal scale formula below 19-17, and toward 

 the obscuring of the stripes, the only objection to the conclusion that 

 eques is very closely related to the following form (sumichrasti) has 

 been eliminated. As will be shown in the description of the latter, 

 there are no appreciable differences between so-called sumiclirasti 

 specimens from Orizaba, Veracruz, and typical eques except in the 

 slightly larger number of scale rows of the latter; a discrepancy 

 that entirely disappears when it is noticed that in the intermediate 

 region, geographically, the scutellation of eques tends to become 

 apparently exactly that of sumiclirasti. On the north we believe 

 that it is directly related to parietalis (see p. 172). 



SUMICHRASTI.b 



Description. — I use this name to designate those specimens, so 

 far recorded only from southern Mexico, that otherwise combine 

 the usual coloration of eques with a reduced scutellation and the 

 usual absence of the dorsal stripe. 



« I can find absolutely no character in which the types and only specimens of 

 Eutaenia aurata Cope (1892, 659-660) and Thamnophis eyrtopsis cydides Cope (1862, 

 299) differ from typical eques specimens. 



b Thamnophis eques sumichrasti (Cope), Proc. Acad. Nat. Sci. Phila., 1866, p. 306. 

 Includes also E. chrysocephala Cope and Tropidonotus godmani GtJNTHER. I use 

 this name advisedly. As before stated, the types of sumichrasti are in very bad con- 

 dition, but they are apparently very similar in coloration to so-called chrysocephala 

 specimens from the same region. Cope always distinguished the former as having 

 19 scale rows and the latter as having 17, but since typical chrysocephala specimens 

 with 17-19-17 scale rows are found inVeracruz, the distinction is not a sufficient one. 

 Since also both forms are characterized by the usual obscurity of the dorsal stripe, I 

 feel justified in concluding that it was upon specimens of this kind that Cope based 

 his description of sumichrasti, which name should, therefore, be the name of the formi 

 Tropidonotus godmani was evidently based on a specimen of this form with a dorsal 

 stripe. 



