120 BULLETIN 61, UNITED STATE!? NATIONAL MUSEUM. 



adhere quite closely to the coastal plain in Mexico, but in the United 

 States it has apparently been able to push out along the rivers, the 

 westward trend of the streams permitting it to cross the plains and 

 prairies, the Mississippi to extend its range well to the northward. 

 East of the Mississi})pi liiver the group has been able to extend over 

 all of eastern United States, the coastal plain leading one section 

 from the coastal plain of Texas and Louisiana into Florida and from 

 here up the Atlantic coast, the other section pushing into the trans- 

 Allegheny States from the Mississippi Valley. It should be noted 

 again in this connection that a reduction in scutellation and size in 

 the group takes place away from northern Mexico, both to the south 

 and east (the extremities of the range of the group), and that the 

 area between the forms, in which a difference in scale formulas is 

 accomplished, is in every case narrow. 



THE ELEGANS GROUP.— (ANGUSTIROSTRIS, MELANOGASTER, SCALARIS, PHENAX, 

 HAMMONDI, ELEGANS, ORDINOIDES.) 



ANGUSTIROSTRIS a 



Description. — If in assembling these forms of garter-snakes I 

 have distinguished a natural group I should be able to support my 

 position by pointing out the lines of relationship between the com- 

 ponent forms. As in the Radix group, I begin with the forms on 

 the Mexican table-land, one of which (angustirostris) also possesses 

 the maximum scutellation for the group. Apparently not over a 

 dozen specimens of this form have been recorded, although it is 

 probably not rare in the region where it is found. 



In appearance it is one of the' most peculiar forms in the genus. 

 The stripes are usually entirely wanting, but the laterals are occa- 

 sionally faintly in evidence on the second or second and third rows, 

 and the dorsal for a short distance anteriorly on the median row. 

 The scutellation in the specimens examined is as follows: Dorsal scale 

 formula, 21-19-17, with occasional variations to 21-2.3-21-19-17 

 and 19-21-19-17; supralabials, 8 to 9; infralabials, 10-11 (9 in one 

 instance); preoculars, usually 3; postoculars, 3 to 4; subcaudals,65 to 

 83; ventrals, 153-163; tail length, .235 to .256. The eye is generally 

 cut off from all but one labial by the anterior prolongation of the 

 lower postocular, but this is not always the case. 



The color above is usually dark olive brown, with six rows of dark 

 brown spots on the scales, distinct in the young, but indistinct or 

 obsolete in the adults. The head is also unicolored above in the 

 adults, wliile in the young it is finely speckled with lighter. Each 

 upper and lower labial is margined with a triangular patch of brown 



o Thamnophis angustirostris (Kennicott), Proc. Acad. Nat. Sci. Phila., 1860, p. 332. 

 This form includes Atomarchus multimaculatus Cope and Chilopoma rufopunctatum 

 Cope. 



