Isotely and C'oralsnakes. 9 



red beiug- separated by iiarrow yellow or whitish margins, the last 

 remnants of the original xauthic ground colonr. 



This handsome dress, seemingly very complicated, is in reality 

 easily evolved and therefore very common. It is the usual dress of 

 Elaps fulvius in Mexico, of E. corallinus and E. hucMeiji in South 

 America, Exactly the same is worn by the aglyphodont Polyodontophis 

 venustissimus of Central America, and by some specimens of the 

 opisthoglyph Erythrolamprus aesculapii in Ecuador; also by the opis- 

 thoglyph Scolecophis aemulus of Batopilas. 



Further changes. The pale yellow or white margins between 

 the black and red are encroached upon by the black. Result an 

 essentially red snake with sharply marked black rings, e. g. Elaps 

 fulvius SE. 3; corapare also with DM. 3b. 



Or, the whole interstitial black pigment shrinks, is encroached 

 upon by the dominant red which next suppresses the yellow margins, 

 until the whole body is red with irregularly shaped, paired or unpaired 

 black spots, the last vestiges of the recessive coloration ; e. g. specimens 

 of E. fulvius var. affinis; specimens of the usually banded Geophis 

 semidoliatus and of G. fasciatus. 



The whole process is beautifully demonstrated by the individual 

 variations of a family young Streptopkorus atrafus which I was lucky 

 enough to find near Orizaba. They all have the usual jet black 

 head and broad collar, divided by a yellow band of variable width. 

 Specimen I was duU red owing to every red scale being slightly 

 tipped with brown. Specimen II was bright brick red with one Single 

 deep black spot on the left side of the neck, covering one scale and 

 a half. Specimen III brick red with many small black spots on the 

 back, but so irregulär that it is not possible to arrange them either 

 in two long series or in transverse pairs. Specimen IV brick red 

 with many rather large black spots, some irregulär, others alternating, 

 others almost meeting in pairs, and some forming complete crossbars; 

 moreover most of the larger spots, and all the bars are margined 

 in front and behind with pale yellow, — The same conditions 

 prevailed among the immature specimens of another family which 

 I found at La Raya, on the confines of the States of Vera Cruz 

 and Oaxaca. 



StreptopJiorus atratus. a small snake which scarcely reaches 

 400 mm in length, ranges from South Eastern Mexico to Ecuador 

 and Venezuela. It is known to vary much. Boulekgee, Cat. 

 Snakes , , . sums up the main variations as follows, 1, Dark brown, 



