C. J. Sundevall on the Wings of Birds. 397 



These different kinds of feathers are : — 



Upper (superiores) , when seated upon the upper side of 

 the wing, and 



Lower (inferiores) upon its lower surface ; and further from 

 the different parts of the arm : — 



Upper-arm feathers (humerales) on the humerus, 



Forearm feathers or merely arm-feathers (cubitales) on 

 the cubitus, and 



Hand-feathers, "Lash-feathers" (Primores, L.), on the 

 hand. 



Upon this terminology we shall have something more to 

 say further on. It is only upon the cubitus that all the 

 different kinds of wing-feathers occur together. 



The structure of the feathers need not here be described ; 

 it does not belong to our subject, and is treated in detail in 

 Nitzsch^s ' System der Pterylographie.^ Nevertheless a 

 terminology of their external structure may not be super- 

 fluous in this place, which will give the opportunity of pro- 

 posing some small changes in the terms employed by Nitzsch 

 in the above-mentioned work, which he did not himself 

 complete. 



The external parts of the feather are as follows : — 



1. Calamus (the quill-tube, fig. 12, a), the transparent, 

 horny part, which is fixed in the skin. 



2. Rhachis (the shaft, b), the part filled with white pith, 

 which bears the vane. On the whole outer side (obverse side) 

 this is clothed with a direct continuation of the calamus in 

 the form of a sharply defined horny lamella. The whole of 

 this side is somewhat convex or flat, without any depression, 

 and scarcely elevated above the vane. The inner or opposite 

 side is considerably elevated above the vane, covered with a 

 peculiar, thinner, and sharply-defined horny lamella, and has 

 a longitudinal impressed line which terminates in the 



Umbilicus [d], or the opening into the interior of the tube. 

 This opening is very small, and is closed by a projecting 

 point of the dried membranous parts remaining in the tube. 

 Fig. 12 shows a small feather, seen from tlic reverse side. 



