144 Letters, Extracts, Notices, ^c. 



cimeiis in the National Museum from Greenland show the 

 widest extremes, which are bridged by connecting specimens, 

 so that it is impossible to definitely separate them. The 

 young retain their streaked plumage until the second fall, as 

 is stated by Newton in the 'Proceedings of the Philadelphia 

 Academy of Sciences' (1871, pp. 96, 97). This author's 

 separation of gyrfalco from islanclicus on the assumption 

 that the head is lighter than the back in one and uniform 

 with the back in the other rests upon a purely individual 

 character, as is shown by my Alaskan series." 



- 1 The Penguhi of the Rio de la Plata. — In his ' Naturalist's 

 Voyage' (chapt. iii.) Darwin speaks of having seen nume- 

 rous Penguins in the estuary of the Rio de la Plata, when 

 approaching Monte Video in the 'Beagle' in July 1832. 

 Mr. W. H. Hudson is also well aware of the existence of 

 Penguins on the coasts of the A-rgentine Republic, and 

 has once seen a dead specimen on the shore near the Rio 

 Negro. I believe the species to be probably the Jackass 

 j_ Penguin [Spheniscus magellaniciis) , but I am very anxious to 

 identify it correctly, and should be exceedingly obliged by 

 any information on the subject. Are there any examples of 

 Penguins from this locality in public museums or private 

 collections ? P. L. Sclater. 



