In the Classification of Birds. 5 
area of origin of the obturator internus has proved to be ; 
and lastly, a few words with respect to the variations ex- 
hibited on the part of the plantar tendons in certain groups 
of birds. 
Let us first, then, turn our attention to the muscles of the 
pectoral limbs; and up to the present time the five following 
named ones have been found useful as characters in the 
classification of the class, or have proved of assistance, when 
Fig. 2.—Same view and corresponding parts of the 
same wing of a passerine bird, Purple Martin, Progne 
subis, (by the present writer). ¢p. l., tensor patagii 
longus; tp. 6., tensor patagii brevis; dt. p., dermo- 
tensor patagii; ¢.m.7r. l.. extensor metacarpi radialis 
longus; ¢., ‘triceps; b., biceps; S. 7?., secondary remi- 
ges (fig. 2 nearly x 2). 
taken in connection with other structures, in determining 
aftinities. 
1. The tensor patagii longus. 
2. The tensor patagit brevis. 
3. The dermo-tensor patagii. : 
4. The bicipital slip to the patagium. 
5. The expansor secundariorum. 
Garrod found all but No. 3 of these present in one bird 
