ai:t. 4 



BIRDS OF THE MENTAWI GROUP RILEY 



Check list of Mentawi birds — Continued 



43 



*' On the islands off the west coast of Sumatra three forms of Hemiprocne longipennis occur: 



(1) Hemiprocne longipennis perlonga (Richmond) on Simalur. Wings long (172-184), head and mantle 

 shining bronzy green, gray of the rump more or less restricted. 



(2) Hemiprocne longipennis ocyptera Oberholser on Nias. Wing shorter (163-175) head and mantle less 

 bronzy than H. I. perlonga, gray of rump more extensive. 



(3) Hemiprocne longipennis thoa Oberholser on the Batu Islands, South Pagi, and probably the inter- 

 vening islands. Wing longer than //. I. ocyptera (173-180), about the same size as H. I. perlonga, but the 

 latter more bronzy green on head and mantle; the rump less extenisvely gray. 



Of Hemiprocne longipennis harterti Stresemann (type locality. Deli, Sumatra), I have not examined 

 enough specimens from Sumatra to comment upon its validity, but specimens from Trengganu, Penin- 

 sular Siam, average smaller, (wing, 154-164), are more bronzy on the mantle and bead, and are darker 

 below than the Nias Island form. 



