474 DR. J. MURIE ON THE DERMAL AND VISCERAL STRUCTURES 
words, he mentions, “I have found these definitely limited powder-down tracts of very 
different forms, numbers, and positions in certain Hawks of the subgenera Elanus 
and Circus, and also in Ocypterus, Crypturus, Eurypyga, all the Ardew and Cancroma.” 
But evidently he has failed to recognize in their distribution a certain relation and 
interdependence between them and the contour-feather tracts and featherless inter- 
spaces, both of which he has so critically minutely worked out and graphically 
described. At all events, it appears as if he had only entered on the threshold of 
their arrangement; for he does not adopt any definite nomenclature as applied to 
them in contradistinction to the feather-tracts and spaces. Indeed his brief remarks 
are confined particularly to the clumps situated on the back and rump of certain genera 
among Accipitres, Passerine, and Galline, and to the additional ventral patches among 
the Gralle. 
The preceding general considerations are meant to introduce the subject of the pro- 
priety of adopting a separate nomenclature to be applied to the powder-downs in contra- 
distinction to the true feather-tracts and spaces. 
If, as I shall attempt to demonstrate, the powder-down feathers have a less or more 
regular distribution within certain limits, other than those pointed out by Nitzsch and 
succeeding observers, it appears to me advisable they should receive individual designa- 
tion in the manner which has been so efficiently employed in the other portions of the 
pterylosis by the aforesaid author. 
Such a matter it is more fitting for skilful ornithologists to decide: but I here make 
the suggestion, leaving it to their judgment to reject or adopt the proposal, which I 
work out, so to say, in a provisional form. 
For convenience’ sake, in comparing the relation of other parts of the pterylosis with 
the powder-downs, and to give uniformity as respects one form with the other, I coin a 
set of terms kindred to and in part derived from those used by Nitzsch in defining the 
feather-tracts and interspaces. 
My plan is simply to apply the term patch, instead of and equivalent to Nitzsch’s 
“tract” and “space,” to those powder-down plumes, whether few, scattered, or aggre- 
gate in number. In this manner the regions, as denominated by Nitzsch, may hold 
good in general, excepting where the name used by him is not strictly applicable to the 
“patch” under consideration. 
It must be remembered, and not lost sight of, however, that the powder-down feathers 
occasionally are ill-defined in their limits. Indeed, oftentimes they are so few, scattered, 
and intermingled with the feather-tracts and spaces, that this doubtless has inclined 
such an accurate observer as Nitzsch to conclude that they possess no regular arrange- 
ment, excepting the lumbar and ventral patches. I trust, though, to show, from their 
disposition and abundance in the Kagu &c., that a probability exists of their not being 
diffused at random, but subject to a plan, or found within guiding lines, as are the 
other feathers. 
