No. 3.] POSITION OF CHAMAA. 493 
although they have, asa rule, a sternum in each species with a 
style to it of their own, yet by the slightest modification it could 
be easily made to assume the pattern of the bone, as we find it 
among most North American Paving. For example, how much 
the bone is alike in two such species as Salpznctes obsoletus and 
Parus tnornatus ! Again, take three such sterna as are offered 
us in the skeletons of Pyrotonotaria citrea, Accentor modularis, 
and J/cterta virens, and how marvellously close is the similarity, 
even to the most insignificant details (barring the one less facet 
on either costal border, in the case of the second-named species) ; 
and if guided alone by their form, how difficult it would be to 
distinguish them without any other assistance! And yet, were 
the sternum of Psaltriparus plumbeus brought up to the size of 
the sternum in the Prothonotary Warbler, we would have no 
difficulty in such a matter, notwithstanding the fact that the 
general pattern in both is the same; and how extraordinary is 
the gentle gradation in form between two such species, in this 
part of their skeletons, with respect to species of intermediate 
affinity ! 
On the Appendicular Skeleton: the Pectoral Limb. — As is 
usually the case, the several bones of the limbs of these small 
passerine birds offer us but a slender list of distinguishing char- 
acters, in any way pointing to the affinities of the species com- 
pared. In Chamea the bones of both extremities appear to be 
completely non-pneumatic, whereas in such a Tit as the Parus 
znornatus both the humerus and femur have air admitted to 
their shafts; and I am not certain but that the long bones of 
the antibrachium and leg are in the same case. Other Tits also 
have the arm and thigh bones pneumatic. The Awmerus in our 
subject is characterized by having a notably straight shaft, and 
for its brevity, as compared with the size of its owner. Its head 
and distal extremity, however, are in harmonious proportion with 
its length ; while the small glenoid cavity of the shoulder girdle, 
intended for its articulation, is re-inforced by a fair-sized os 
humero scapulare, in which it agrees with other species and 
genera before me. 
_ Both bones of the antibrachium, the vadzus and ulna, are like- 
wise very short and very straight. This may be best appreci- 
ated by stating the fact that the radius in Psaltriparus plumbeus 
comes within a hair’s breadth of being fully as long as that bone 
