Shufeldt on the Osteology of C inclus Mexicanus . 221 
Cooes, in his Osteology of Colymbus tor qu at us , leaves no doubt 
in our mind how he regards this projection of the tarso-metatar- 
sus ; this author says: — “The process of bone representing the 
os calcis , rises at the superior end of the bone, on its posterior 
aspect, as a very conspicuous crest.” 
Professor Morse, in his Tarsus and Carpus of Birds (Ann. Lyc. 
Nat. Hist., N. Y., Vol. X, 1872), speaks of the centrale, but not 
in connection with this process. 
In the chick of Centrocercus I found that the centrale did not 
indude this process, consequently in my Osteology of the Tet- 
raonidce (Bull. U. S. Geol. Surv., Vol. VI) I declared that 
this process had nothing whatever to do with the os calcis, and 
in the osteology of Lanins, termed it the tendinous process, from 
the fact that the flexor tendons in so many birds either pass 
over or through it. Now our young of Cinclus mexicanus, 
just before it leaves the nest, has its metatarsal bones still ununi- 
ted, and crowned by a separate segment that has apparently ossi- 
fied from one single centre, a segment that not only includes the 
centrale, but the entire process of which we have been speak- 
ing. So between Cinclus and Centrocercus we must still look 
for other forms to throw light upon this problem. The subject 
is an extremely engaging one for the ornithologist to look into 
and investigate. 
The shaft of the tarso-metatarsus of this bird develops after the 
usual rule set forth in works upon the subject, and the same may 
be said of the phalanges. 
The writer only hopes that his sketch, necessarily brief, and 
far from being exhaustive, will have at least the tendency to in- 
duce other ornithologists to record their observations upon this 
subject whenever the opportunity offers. 
Our studies, as far as we have carried them, seem to point 
pretty conclusively to the fact that our American Dipper is quite 
closely related to the genus Siurus, and not far removed from 
some of the Wrens. 
