No. 500] NOTES AND LITERATUEE 



555 



1. Thamnophis megalops (Kennicott). "1 



2. Thamnophis marcianus (Baird and Girard). | 



3. Thamnophis radix (Baird and Girard). V Radix group. 



4. Thamnophis butleri (Cope). 



6a. Thamnophis angustimsl ris m, htnuqastcr ( Peters). 



7. Thamnophis scalaris (Cope). 



8. Thamnophis phenax (Cope). I 



9. Thamnophis hammondi (Kennicott). ^Elegans group. 



10. Thamnophis ordinoides (Baird and Girard). 

 10a. Thamnophis ordinoides elrqans (Baird and 



Girard). 



11. Thamnophis eques (Reuse). ] 

 11a. Thamnophis eques sumiehrasli (Cope). 



12. Thamnophis sirtalis (Linne). Isirtalis group. 

 12a. Thamnophis sirtalis parietalis (Say). 



12b. Thamnophis sirtalis coneinuus (Hallowell). J 



Of these groups he states (p. 186) that the sirtalis group "is 

 without doubt the least diversified." since its members are given 

 by most herpetologists only subspecific rank, owing to their evi- 

 dent intergrading. 



Later on in the paper, in his "Discussion of Origins," he 

 gives his reasons for believing that the genus Thamnophis had 

 its origin in northern Mexico, and not in southeastern United 

 States, as held by Cope and Brown. The four "groups" are 



"Method of Evolution of the Forms" (p. 192) : "If the range 

 of the forms in the different groups of garter-snakes be care- 

 fully examined it will be found (1) that the different forms of 

 the same group are found in different geographical regions, 

 characterized by different environmental conditions; (2) that 

 the area along the common boundary of two forms of the same 

 group, where transition in characters takes place, is relatively 



