346 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



Two styles of coloration are exhibited by the snakes of 

 Barrington. Seven specimens (Nos. 10151, 10152, 10183, 

 10213, 10214, 10217, 10226) are striped, while eight (Nos. 

 10147, 10150, 10182, 10215, 10216, 12055, 12060, 12061) are 

 spotted. The difference here, as on Indefatigable, is due 

 neither to age nor sex. It must be regarded as a form of 

 dichromatism. In the spotted specimens, the longitudinal light 

 stripes are represented only by a pair of short longitudinal 

 yellowish-white blotches on the nape. In striped specimens, 

 the light stripes are confined to the scales of two rows. In all 

 specimens, the light nuchal blotches or the longitudinal stripes 

 end anteriorly sharply and definitely several scales behind the 

 parietals. In all spotted specimens, the dark brown spots or 

 blotches become obsolete posteriorly ; while, in all striped speci- 

 mens, the light bands extend to the tail. 



General Remarks. — It is probable that larger series may 

 result in the recognition of subspecies of Dromicus dorsalis. 

 Even now the peculiarities of coloration, with the frequent 

 reduction in temporals and postoculars, almost justify the 

 separation of the Barrington Island snakes. The serpents of 

 Indefatigable and Seymour appear to differ from those of the 

 other islands in the possession of a greater number of uros- 

 teges, but so many of the specimens have lost the tips of their 

 tails that more evidence is needed. Inconstant as the differ- 

 ences may prove to be, I believe that the following tentative 

 key may prove useful to future investigators. 



a. — Stripes or nuchal blotches ending definitely several scales behind par- 

 ietals ; stripes narrow. 



Temporals usually 1+1; postoculars often 1; urosteges fewer. 

 Barrington. 

 a.2 — Stripes or nuchal blotches usually continued forward to parietals; 

 stripes wider. 

 b. — Urosteges more numerous; temporals usually 1+2; spotted or 

 striped. 



Indefatigable and Seymour. 

 b.2 — Urosteges fewer; temporals usually 1 + 1; striped. 

 James and Jervis. 



We do not know why so many of these snakes have lost the 

 tips of their tails, but Mr. Slevin reports that the mocking- 

 birds were observed picking at the tails of Tropiduri until they 

 fell off and could be eaten. 



