396 J. Wyman on Fossil Bones from the Red Sandstone, &c. 
matrix is the fragment of a stzth having the articulating processes 
imperfectly preserved. 
f these six imperfect vertebree only that first described, and 
the piece behind it offer distinctive characters of any importance. 
The presence of an inferior spinous process shows that it belonged 
to the caudal series; the existence of an anterior concavity, and 
the presence of a superior transverse process coexisting with an 
inferior spinous process are essentially reptilian features. In fishes 
the superior transverse processes are always deficient, and the in- 
ferior ones alone exist; these in the tail bend down to form the 
inferior spinous processes. If this bone is the one referred to by 
r. Porter as a “tail bone” his view as regards the kind of ver- 
tebra was correct, though he gives no reason for his conclusion. 
In addition it may be stated that it is a caudal vertebra of a Sau- 
rian reptile, to which it corresponds in the shape of the body and 
the transverse processes, and more nearly to those of the Croco- 
is that of hollowness, and this in two cases is quite remarkable. 
In one of them we have a transverse fracture of what appears to 
be a cylindrical bone ; the exposed fractured end is oval, measures 
one and one tenth of an inch in its long and six tenths in its 
short diameter; the cavity is very large, without cancelli and the _ 
walls of the bone are only one tenth of an inch in thickness. 
Near to this in the same mass of the matrix is another fragment 
which is exposed in transverse section as well as on a portion of 
its lateral surface. In its transverse section, it is more compressed 
than the preceding, but has equally thin walls and no cancelli. 
The whole fragment bears some resemblance to the upper extrem- 
ity of the humerus of a bird,* distorted by pressure. ‘The large 
size of the cavity and the thin walls lead us to compare this and 
the preceding specimen with the remains of birds, for it is among 
these alone that the cavities become proportionally so large aud 
- the walls so thin. Still it must be remembered that some rep- 
tilian bones are hollow. The Iguanodon, Pelorosaurus and Hyl@0- 
saurus described by Dr. Mantell, which had medullary cavities 1n 
the humerus and femur, but in them the walls were proportionally 
very much thicker, and the medullary canal was quite short. 
Several other pieces of matrix contained fragments of bone 
which were hollow and with thicker walls; but they were too 
much injured to allow of determination. 
* Its resemblance to a humerus was noticed by Prof. Silliman in the note append: 
ed to Mr. Smith’s communication—in vol. ii, of this Journal 
