26 Proceedings of the Biological Society of Washington. 



Specimens from Trinidad are said by Bangs and Penard to show an 

 excess of chestnut edgings to the feathers, particularly posteriorly, and 

 according to these authors (Bull. M. C. Z., LXIII, 1919, p. 38) should be 

 referred to Ostinops decumanus insularis Dalmas, of Tobago. Paria 

 Peninsula birds are also strongly margined with chestnut posteriorly, but 

 a Tobago male is darker and has as little chestnut as a male from Para- 

 maribo. (See also in this connection, Hellmayr, Nov. Zool., XIII, 1906, 

 p. 19.) 



Bolivian specimens are intermediate between those from Colombia and 

 the Paria Peninsula and a series from Chapada, Matto Grosso, is of a 

 browner tone than those from Bolivia. Possibly several races, distin- 

 guished by such differences of degree as I have here briefly referred to, 

 may in time be recognized, but in the absence of adequate series from 

 Tobago, Trinidad, and the Guianas, I am not in a position to deal with 

 this phase of the subject. 



The 108 specimens of Ostinops decumanus which I have examined, and 

 of which 102 are contained in our Museum collections, do show, how- 

 ever, that in southern Peru, Bolivia, and southwestern Brazil, this species 

 is subject to a variation of which a slight trace is shown by only one of 

 our 44 specimens from the Amazon northward. 



In brief, this variation consists of the presence in varying numbers and 

 scattered more or less irregularly throughout the plumage of the body 

 and wing-coverts, of feathers which are wholly or in part yellow and 

 rarely white. Presented in a single individual, or even a number of indi- 

 viduals, such variation would be considered as pathological and termed 

 albinistic or xanthochroic. Dr. Allen, for example, in commenting on its 

 occurrence in a series of birds from Matto Grosso said: "It is evidently 

 an abnormality analagous to albinism." When, however, it is exhibited 

 by a large proportion of the birds from a wide area and by every bird in 

 a large series from an extended area, it presumably cannot be considered 

 as adventitious but is apparently the result of a cause or causes which 

 are or have been operative over an extensive region. Whether this varia- 

 tion may be attributed to environmental influences, past or present, to 

 atavism or to mutation, I am unable even to surmise; it is, however, 

 clearly not individual, but apparently racial, and as such, in spite of its 

 variability and unlikeness to those differentiations of degree which are 

 so commonly associated with climate, the birds occupying the area in 

 which it occurs should, in my opinion, be distinguished by name from 

 those inhabiting a region in which this variation is practically unknown 

 Hence, as a means of giving a "handle to this fact," I suggest naming the 

 form of Ostinops decumanus found in southern Peru, Bolivia and Matto 

 Grosso, of southwestern Brazil, 



Ostinops decumanus maculosus, new subspecies. 



Subspecific characters. — Similar to Ostinops decumanus decumanus (Pall.), 

 but averaging smaller and with a shorter bill, the general tone of colora- 

 tion browner and with a variable number of feathers wholly or in part 



