No.412.] SMALLER NORTH-AMERICAN SHRIKES. 275 
B. Measurements of Variable Characters. 
I. Linear Measurements. Length of Wing. — The shortest 
distance between the wrist and the tip of the wing was 
measured with a pair of dividers, the wing being folded natu- 
rally at the side of the body. The left wing was taken in every 
case for the measurement. 
Length of Tail.— This measuremént was made from the 
papilla of the uropygial gland to the extreme end of the tail 
feathers. One arm of the dividers was placed with its point 
resting on the anterior face of the papilla. On account of 
mutilation and frequent difficulty in finding the papilla, the 
measurement has often to be omitted. Great precision cannot 
be obtained, as there is irregularity in the relative position of 
the papilla in the drying of the skin, and there is also usually 
some wearing away of the distal ends of the rectrices. When 
the latter were much frayed no measurement was attempted. 
Length of Bill.— The only satisfactory method found for 
measuring the length of the bill was to take the shortest dis- 
tance between the nostril and the distal apex of the upper 
mandible. The point of one arm of the dividers was placed 
against the most distal face of the nostril. I have had to make 
allowance in some cases for the wearing away of the distal 
apex of the upper mandible, though the amount of wear is too 
small to materially affect the measurement. 
Depth of Bill. —'The greatest dorso-ventral diameter of the 
bill near its base was determined. There is considerable lia- 
bility to error here on account of lack of uniformity in the 
articulation of the mandibles in the dried skin, and I found it 
necessary to reject quite a number of skins on this account. 
2. Curvature of Bill. — This is a character of the distal half 
of theculmen. Its quantitative expression is a matter of some 
difficulty, for we have here a curve which is not the arc of a 
circle nor a parabola, nor does it correspond to any geometrical 
figure. Then, too, the form and size of the bill are such as to 
render it impracticable to make precise measurements directly. 
To meet the latter difficulty it was decided to try to trace on 
paper the enlarged projection of the outline of the bill. After 
