LITHORNIS VULTURINUS, 5d3 
Fig. 233. 
Sacrum of a Bird, eocene clay, Sheppey. Nat. size. 
Figures 233, a and sp, give two views of the second 
ornitholite from Sheppey, alluded to in the preceding 
section: in the side-view, a, ten vertebree are anchylosed 
together, and the under view, 8, shows the complete con- 
fluence of the vertebral bodies. The long sacrum thus 
formed is peculiar to birds, and relates to the unfayvour- 
able position of a horizontally disposed trunk for support 
on a single pair of limbs,—compensation being made by 
the great extent of the axis of the trunk, which is grasped, 
as it were, by the iliac bones, and the weight transferred 
by these to the heads of the obliquely-placed thigh-bones. 
As all birds, whether they have the power of flight or not, 
are bipeds and prone, the long sacrum is common to all, 
and its structure does not present such well-marked modi- 
fications as to permit any satisfactory deductions from the 
present mutilated specimen of the precise position in the 
feathered class of the ancient bird which it represents. 
The specimen itself forms part of the choice collection 
of J. S. Bowerbank, Esq., F.R.S. 
