STUDIES OE THE MACROCHIRES. 
313 
Passerine pattern for the hyoid arches, and I have elsewhere 
figured them for that form *. 
The sclerotal plates of the eye are composed of separate little 
pieces of bone in all of these birds of which we have been speaking ; 
but in old specimens in some of the Tyrannidoe I have often 
noticed their tendency to anchylose together, notably in the 
genus Sayornis. 
Passeres usually have a small sesamoid bone at the angle of 
the jaw. I have failed to find it in Ampelis, but would prefer 
examining more specimens before positively announcing its 
absence. It seems to be invariably present where indicated in 
all of the higher Thrushes. 
23. Of the remainder of the Axial Skeleton . — It will be pro- 
bably a very long time before a sufficient number of the vertebral 
columns of existing birds have been examined, to ascertain with 
certainty whether the vertebrae composing them are constant 
for the several divisions and for the species. When this has 
been done, and the exact averages ascertained, the result will 
be no doubt important in assisting to decide doubtful points 
in classification 
The figures recorded in the subjoined Table have in every case 
only been set down after carefully counting the segments two 
or three times. With respect to the number of vertebrae in 
the consolidated sacrum of the pelvis, they are here counted 
in the adult bird, and consequently must be taken cum grano 
sails, though I believe them to be quite correct. 
I am inclined to think at present that the number of free 
coccygeal vertebrae are liable to vary even in representatives 
of the same species. 
This Table, of course, could easily have been made far more 
extensive, but in that case would have overstepped the object at 
present in view. I trust, however, that those who at any time 
may be engaged in examining the structure of birds will record 
such data as I have attempted to do here, and only after the most 
careful counting. To do this, reliance can be placed only upon 
spirit specimens, or recently killed birds, where there has been 
no possibility of any of the vertebrae having been lost. 
* Shufeldt, It. W., “ Osteology of Lanius luclovicianus excub itor ides,” Bull. 
U.S. Geol. and Geog. Surv. of the Territories, vol. vi. pp. 351-359, pi. xiv. 
fig. 101. Also same plate and figure in the author’s collected memoirs 
‘ Contributions to the Anatomy of Birds.’ 
