STUDIES OF THE MACROCHIRES. 
315 
sternum may sometimes assume a different form even for the 
same species *, which I have never found to he the case in the 
pelvis. 
In PL XVIII. fig. 7 is represented the superior or dorsal 
view (double the size of life) of the pelvis of Ampelis cedrorum ; 
it shows very well indeed the general form and characters of this 
bone as it occurs among the Passeres. Considerable interest 
attaches, however, to an examination of a transition series of 
pelves through the Passerine group of birds into other orders 
wherein marked differences are to be found. 
Now in such a bird as Sarporhynchus rvfus , for instance, or 
any of its genus, the pelvis, when viewed from above, has pretty 
much the same form as it has in Ampelis ; but all the processes 
are more prominent, and all the ridges and crests more con- 
spicuous and defined. This lends to the bone quite a striking 
appearance in these higher Thrushes. But as we pass through 
the members of the Oscinine group and into the Clamatores, this 
bone, although it retains its general pattern, gradually loses 
this peculiar angularity, and gains in breadth while it becomes 
comparatively shorter in the longitudinal direction. My meaning 
will be made clearer when we come to examine, further on, the 
pelves of the Swalloivs and Sivifts. 
As to the characters of the pelvis in Ampelis, we are to note 
that, anteriorly on its dorsal side, the inner margins of the ilia 
are widely separated from the crista of the sacrum ; that the pre- 
and post-acetabular areas are about of equal dimensions, that the 
former are concave outwards, while the reverse condition obtains 
with the latter; that the “ sacrum ” upon this view is roughly 
lozenge-shaped, and that interapophysial foramina of varying 
sizes may be found to exist in it. 
Upon the lateral aspect it is to be observed, that not only is 
the acetabulum (as it invariably is in birds, I believe) completely 
surrounded by bone, but the ischiadic, the obturator, and the 
obturator space are true foramina, or at least are entirely en- 
circled by bone. In Tyr annus verticalis the ischium fails to 
meet the post-pubis between the obturator foramen and obturator 
* For examples of this see my remarks upon the different forms of sternum 
in the Cathartidge, “ Osteology of the Cathartidaj,” in Contributions to the 
Anat. of Birds, from U.S. Geol. and Geog. Survey, 18S2 (Hayden’s 12th 
Annual), pp. 771, 772, where four figs, of sternum of C. aura are given. 
FINN. JOURX. — ZOOLOGY, VOL. XX. 25 
