Letters, Announcements, i§c. 481) 



Heligoland, August 29, 1878. 



Sirs, — As perhaps it may interest soroe of the readers of 

 ' The Ibis/ I beg leave to inform you that on the 20th inst. 

 Larus affinis, Reinhardt, = L. cachinnans. Pall., =L. borealis, 

 Brandt, was shot here, being the first instance of its capture off 

 this island. The coloration of the back and outer wing- 

 coverts forms an exact middle shade between the slaty black 

 oiL.fuscus and the light grey of L. argentatus. The specimen 

 being in the moult for its winter-dress, the marks on the 

 feathers of the neck appear darker than those of any Gull I 

 know of; in fact these arrow-shaped marks may be termed 

 pure black. 



About the identity of the species no doubt whatever exists, 

 as I have been able to compare the specimen with one of L. 

 affinis in my possession, obtained by Dr. Otto Finsch on the 

 Ob during his recent Siberian excursion. 



I am, yours &c., 



H. Gatke. 



Sirs, — Through the kindness of Dr. Giinthcr I have been 

 entrusted with the preparation of the volume of the Cata- 

 logue of Birds containing the Sylviidse, a group of which the 

 British Museum contains an excellent series from all parts of 

 the eastern hemisphere. In attempting to arrange the various 

 genera belonging to this subfamily, I have been obliged to 

 treat some of them in a rather summary manner ; and I ven- 

 ture to bring a few of my supposed discoveries before the 

 readers of ' The Ibis,' in the hope that their criticisms may 

 confirm or dispel my doubts. 



"Whilst describing the species of the genus Acrocephalus, 

 I found that A. insularis (of which I have already expressed 

 my opinion that A. fasciolatus was the young) was extremely 

 aberrant. Firstly, it is the only Acrocephalus in which the 

 young bird is decidedly yellow on theunderparts. Secondly, 

 it is the only species in that genus in which the rictal bristles 

 are too small to be discernible with the naked eye. Thirdly, 

 its tail is much more rounded than that of any of its com- 

 panions. And fourthly, it is aberrant in having the upper 



