176 BULLETIN 61, UNITED STATES NATIONAL MUSEUM. 



and the adjoining part of British Cohimbia; in which case the name 

 concinnus Hallowell (1852) takes precedence over inckeringi Baird and 

 Girard (1853). 



As stated under iMrietalis, variations in color occur which are 

 indistinguishable from some of those of that form. Thus, the black 

 pigment on the sides may be disposed as two black bands separated 

 by a red one, and it was upon a specimen of this kind from Puget 

 Sound, Washington, as well as the two from Pitt River, California 

 (p. 171), that Cope based his subspecies tetrataenia. Similarly, when 

 the dorsal stripe occupies one and two half rows, as it occasionally 

 does, the specimens are very similar to dark specimens of imrietalis 

 from Montana, and in fact one of the type specimens of trilineata was 

 a concinnus from Fort Townsend, Washington. 



Ajfinities. — Concinnus grades directly into i)arietalis through dark 



specimens of the latter (the phase trilineata) in the Cascade range. 



It has no direct relationship with ordinoides, as may be seen by the 



scutellation, for we have shown that ordinoides, has generally less 



than 19-17 scale rows, while the variations above this number in the 



latter indicate that it is derived from a form with a larger formula 



than 19-17. 



SIR TALIS, a 



DescrijJtion. — This form is one of the best known in the genus, 

 probably owing largely to the fact that it is very common in a thickly 

 settled region. At the present time the material available for study 

 numbers nearly as many specimens as that of all the other forms 

 combined. 



The lateral stripe is always on the second and tliird scale rows, and 

 the eye is large. The dorsal stripe usually occupies the median and 

 halves of the adjacent rows, is frequently narrower and occasionally 

 wanting. The dorsal scale formula is practically always (in 598 out 

 of 600 specimens examined ; seep. 181) 19-17; the supralabials nearly 

 always 7, occasionally 8, rarely 6; the infralabials 10, occasionally 

 9 or 11, The oculars are usually 1-3, often 1-4, more rarely 1-2; 

 the siibcaudals 54 (female) to 84 (male); the ventrals 137 (female) 

 to 167 (male). Tail length .192 to .262. 



The ground color above varies from light green, light greenish 

 olive, or light olive brown to dark greenish olive, dark olive brown, 

 brown, or black. The first row of scales is generally (but not always) 

 much lighter than above, but still somewhat darker than the second 

 and third rows. There are two rows of well-defined spots (rarely 

 fused) on the skin between the lateral and dorsal stripes, and these 

 usually cover more or less of the involved scales (exclusive of the 



o Thamnophis sirtalis (Linnaeus), Syst. Nat., 10th ed., I, p. 222. Includes Coluber 

 ordinatus Linnaeus, Eutaenia sirtalis graviinea Cope, E. sirtalis obscura Cope, E. sir- 

 talis semifasciata Cope, and E. sirtalis pallidula Allen. 



