.\o. 2179. 



VARIATION IN GARTER SNAKES—THOAIPSON. 



365 



NOTE ON SCALE FORMUL.\ IN THAMNOPHIS PARIETALIS (S\Y) \ND 

 THAMNOPHTS COCCINUS (HALLOWELL). 



Another species of garter snake found in the same region with T. 

 ordinoides is TJiamnopMs parietalis (Say) 1823; this form is note- 

 worthy in possessing but one type of squamation, there being 19 rows 

 anteriorly and 17 posteriorly. As this formula is a fairly prevalent 

 one in T. ordinoides it will prove of interest to compare a small set of 

 each species from the same locality. Specimens have been chosen 

 from Skaggs Springs, Sonoma County, California, owing to this place 

 being approximately in the middle of the area occupied by T. 

 ordinoides. 



SKAGGS SPRINGS, SONOMA COUNTY, CALIFORNIA. 

 T. ORDINOIDES. 



T. PARIETALIS. 



28026. 

 28023. 

 28028. 

 28027. 

 28022. 



Male..., 

 Female 

 ..do.... 

 ..do.... 

 ..do.... 



157 

 151 

 154 

 157 

 157 



100 90 



89 88 

 80 82 

 84 85 



90 87 



This table shows that there is a tendency in T. parietalis for the 

 19-row zone to be continued a little further down the body. This, 

 however, is merely a slight difference in the averages of two small sets. 



The only remaining species found along the Northwest Coast is T. 

 coccinus (Hallowell) 1852, this also presents the one scale count of 

 19-17. 



TRASK, TILLAMOOK COUNTY, OREGON. 



