mm the Classification of Birds. 13 
OF THE MUSCLES IN THE THIGH OF BIRDS. 
There are five muscles in the thigh which have proved to 
be more or less useful in the classification of Birds. These 
muscles are the following, and four of them I have desig- 
nated by the letters which were used by Garrod in his my- 
ological formule. 
The ambiens, 
The femoro-caudal, 
The accessory femoro-caudal, 
9%. The semitendinosus, 
10. The accessory semitendinosus, 
CO TO 
RS ea 
We know of no bird in which all five of these muscles 
are absent, or even of one which lacks the last four in the 
list. 
According to Garrod, ‘‘when these four muscles are 
present in a bird the formula, AB. XY expresses the fact; 
when any one is absent, that such is the case is indicated 
by the omission of the letter representing it. Thus the for- 
mula A. XY indicates that the accessory femoro-caudal 
muscle only is absent; AB. X that the accessory semi- 
tendinosus is missing; A.X that the femoro-caudal and 
semitendinosus only are te be found; and A that the fem- 
oro caudal alone is present.” 
This eminent anatomist applied these myological formule 
to a classification of the entire group of existing birds, and 
fully discussed the matter in his work in the most masterly 
manner in so doing, but it will be impossible to enter upon 
any such field here. In my own opinion, however, I am in- 
clined to believe that Garrod’s classification stands in need 
of a very thorough overhauling in many of its aspects; by 
this I mean that ina vast number of cases we are not in 
possession of the requisite knowledge of the entire structure 
of certain forms as to warrant one retaining them where 
Garrod has placed them. In other words, these myological 
formule, as time goes by, and our knowledge of avian mor- 
phology widens, will surely prove very useful in taxonomy, 
but they can only be employed with safety when taken, as 
one set of characters, in connection with all the others that 
