e 
686 GEOLOGICAL SURVEY. OF THE TE&RRITORIES. 
a pelvis in these birds that will be described further on. We find ina 
specimen of Canace canadensis, for which we are greatly indebted to Mr. 
Manly Hardy, of Brewer, Me., where the sacro-iliac anchylosis is so per- 
fect, and original land-marks so obscure, that one might easily imagine 
the pelvis in this individual as being developed from a very much fewer 
number of ossific centres. The caudal vertebre number five in all the 
Grouse except Cupidonia and Pediecetes, these birds each having dis- 
tinetly six apiece. We would especially call the reader’s attention to this 
fact, because when we come to discuss the pelves of these two birds, and 
recapitulate general skeletal data, it will be found that, as far as osteo- 
logical similarities are concerned, they come very near to each other. 
The coccygeal vertebre, otherwise, in common with the pygostyle, show 
very few differences worthy of record. In Ortyx and Lophortysx there are 
but four caudal vertebre and the pygostyle is markedly acute and long. 
Occasionally the last segment is but feebly developed, as in Lagopus, 
where it may be a mere nodule; and in Bonasa, too, sometimes a sixth 
vertebra can be be found, but usually requires force to detach it from 
the pygostyle, and in our specimens seems to be one of those that origi- 
nally formed that bone—though we do not deny in the face of such evi- 
dence that specimens of the Ruffed Grouse may be found that possess 
six of these vertebra. 
Of the Scapular Arch and the pectoral limb.—This arch, with its con- 
comitant, could have, with all propriety, been described in connection 
with its vertebra, but so distinct has it become, and so far removed in 
order to assist in carrying out such a notorious function as the bird’s 
flight, that the author prefers to follow the general ruling of others by 
discussing it separately. Nothing could be more entertaining in the 
whole range of osteological research and study than the contemplation 
of the various avian shoulder girdles, with their attached wing bones, 
particularly the former, as exemplifying the law of equilibrium between 
a bird’s habits, the never-varying part it is to play in nature, and its 
skeleton or the framework that has been given it to carry that part out. 
This thought invariably enforces itself upon me in every instance after 
an examination of a collection of clavicles of different species of birds. 
It seems that there could not be an equipoise established anywhere in 
living nature more thoroughly compensatory than that ’twixt a bird’s 
power and mode of flight, and its scapular arch and other bones about 
the chest—to meet it, more essentially the clavicles. See the broad, ex- 
cessively pneumatic, yet robust, clavicular arch in any of the genus Ca- 
thartes, birds that sail aloft for hours apparently without fatigue, or the 
very similarly shaped arch in the Canada Goose, but in the latter for 
a very opposite style of sustained flight is non-pneumatic; the feeble 
and often ununited arch in Speotyto, a bird with scarcely any preten- 
sions to being a good flyer at all; in short one would, having a thorough 
knowledge of a bird’s habits, be, in the vast majority of instances, able 
A sess very near as to the pattern of the furculum he would expect to 
nd. | 
Now we have seen, in reviewing the skeletons of the Grouse, that in 
many points some of the species, if we disregard size, similate each 
other very closely, as for instance in the various sterna and vertebre. 
The clavicles of these birds form no exception to this rule, as far as 
1The number of caudal vertebre present or absent in any species must not be over- 
rated as a character, as the segments are liable to vary. I once heard it said that the 
number of true caudal vertebre, including those that went to form the pygostyle, 
ought to equal the number of pairs of feathersin the bird’s tail, judging from the ar- 
Tangement as found in Archeopteryx. 
