105 
THE ANATINE GENUS NYROCA AND ITS NEAREST ALLIES. 
HarrY ©. OBERHOLSER. 
The following pages present the results of an investigation, begun many 
years ago, into the generic relationships of the ducks commonly included 
in the genera Nyroca Fleming (Marila auct. ree.) and Fuligula Stephens. 
These species are: 
Nyroca fering (Linnaeus ) 
Nyroca americana (Eyton) 
Nyroca valisineria (Wilson) 
Nyroca baeri (Radde) 
Nyroca nyroca (Giildenstiidt ) 
Nyroca innotata Salvadori 
Nyroca australis Eyton 
Nyroca brunnea Eyton 
Nyroca nation’ (Sclater and Salvin) 
Nyroca erythrophthaltma (Wied) 
Fuligula marila (“Linnaeus ) 
Fuligula affinis Eyton 
Fuligula fuligula (Linnaeus) 
Fuligula novaeseclandiae (Gmelin ) 
Fuligula collaris (Donovan). 
Of the fifteen species thus comprised, we have examined all but two 
Nyroca innotata and Nyroca nationi. Study of the structural characters of 
these birds has resulted in the discovery of some hitherto unnoticed char- 
acters, which indicate that to include all these species in a single genus 
would be manifestly improper, and that in view of important differences. 
some additional genera need recognition. The characters here used as 
generically diagnostic are constant and trenchant so far as it has been 
possible for us to verify them, and a number of other characters we have 
omitted because they fail to come up to this standard. It is becoming fairly 
well understood that many differences that are apparently good generic 
characters fail when several individuals of a species. or when species of 
other supposed generic groups are critically examined: and while a mere 
abnormality in a single individual can not be held as invalidating a gen- 
eric character, it is quite evident that a character which is not practically 
constant in all individuals of a species can searcely be usable in the diag- 
nosis of a genus. It is evidently thus unsafe to base generic characters on 
examination of a single specimen of a species. but sufficient examples should 
be examined to eliminate the factor of individual variation. As in many 
ducks, so in the birds at present under consideration, the form, shape, and 
proportions of the bill are of prime importance as the indicators of generic 
relationships. Of other characters made use of in the present connection, 
those of the relative proportions of the wing and of inner toe with claw, 
compared with the exposed culmen, are apparently of most importance. 
While coloration as a primary generic character is of little or no value 
among these ducks, it is of interest to note that the generic Classification 
