2 20 Siiufeldt on the Osteology of C Indus Mexicanus. 
from the shaft in the adult, very much as I figured them in 
Lanius. 
Such of my readers as have read my account of the develop- 
ment of Centrocercus in the Osteology of the 7 'etraonidce , will 
remember what we had to say in regard to the lower end of the 
tibia and its growth, and also all that Professor Morse has done 
for us in that direction. The specimen we have of the young of 
Cinclus does not admit of the demonstration of the intermedi- 
um; the fibulare and th o. tibiale seem to ossify separately, how- 
ever. We must admit, then, that in this instance we are no nearer 
solving the problem of the homologies of the avian tarsal seg- S 
merits than we were before, but a little light at least is thrown on 
the subject when we come to examine the next bone, the tarso- 
metatarsus. 
In nearly all birds this bone has at the back part of its upper j 
end a tuberous process, amalgamated with the shaft in the adult, 
that assumes various forms in different members of the class. 
This bony process has -long been regarded with suspicion, as to 
whether it was one of the ankle or rather tarsal bones or not. 
Let us hear what a few of the authorities have to say in this 
matter. Professor Owen tells us in Vol. II of his Anatomy of 
the Vertebrates, when speaking in general terms of this process, 
that : “One or more longitudinal ridges at the back of the upper 
end of the metatarsal are called ‘calcaneal’ ; they intercept of 
bound tendinal grooves which, in some instances, are bridged 
over bv bone and converted into canals; the ridges may be ex- 
panded and flattened.” This would lead one to think that the 
Professor might regard this process as the homologue of the os 
calcis, a tarsal bone. 
Professor Huxley, in his Anatomy of Vertebrated Animals, 
page 254, tells us, in speaking of this process, that: “Again in 
most birds, the posterior face of the proximal end of the middle - 
metatarsal, and the adjacent' surface of the tarsal bone, grow 
out a process, w^hich is commonly, but improperly, termed “cal- 
caneal.” The inferior surface of this hypo-tarsus is sometimes 
simply flattened, sometimes traversed by grooves or canals, for 
the flexor tendons of the digits.” 
Mivart says, When referring to birds: “Thus no projection 
corresponding with the tuberosity of the os calcis exists in this 
compound bone.” (Elementary Anatomy, p. 206.) 
