366 



PROCEEDINGS OP THE NATIONAL MUSEUM. 



This table shows that the IV row does not extend quite so far down 

 the body as in parietalis. 



SUMMABY OF SCALAE FORMULAS IN GENUS THAMNOPHIS. 



Doctor Ruthven recognizes 19 species of garter snakes in North 

 America. Among these there are known 11 distinct combinations 

 of scale row counts. The occurrence of the various combinations 

 among the different species may be seen from the following table: 



Inspection of this table shows that the formula of 19-17 is the 

 most frequent, as it occurs in 12 species; also that there are eight spe- 

 cies with only one scale row count, which in these cases is regularly 

 one of the following thi-ee: 21-19-17, 19-21-19-17, or 19-17; and, 

 finally, that in TTiamnophis ordinoides, there are to be found twice as 

 many combinations as are to be seen in any of the other species. 



If ordinoides is a valid species it offei-s an example at variance with 

 the prevaihng condition in which it is the species with the widest 

 ranges that vary the most, for ordinoides has one of the smallest areas 

 of distribution in the genus. If the converse is true, which is most 

 probable, and it ultimately proves to be inseparable from elegans, it 

 will then conform to the rule in having a wide distribution and a large 

 variability. 



The handling of large series of garter snakes will inevitably result 

 in bringing about a readjustment and broadening of one's concept of 

 what may be implied by Wallace's phrase: "The variability of a 

 species in the state of nature." 



