1900] = HAY—VERTEBRATES OF CARBONIFEROUS AGE. 121 
One important character exhibited in the specimen before me is 
the presence of ribs. The original specimen appears not to have 
exhibited these ; and Prof. Cope concluded that they were really 
not present in the animal, and on this character more especially 
founded for it the order Xenorhachia, a group which he later 
abandoned. The ribs of Amphibamus are very slender, rather 
long and curved, expanded at the proximal end, and with the dis- 
tinct appearance of having been double-headed. In this respect it 
differs markedly from Sranchiosaurus, as described and figured by 
Fritsch, in which the ribs are short, stout, straight and single- 
headed. The number of pairs of ribs I am not able to determine 
with exactness. ‘They are seen to approach to within 7 mm. of the 
head and to within less than this distance of what I regard as the 
sacral region. I make out the existence of at least twelve pairs, and 
there were evidently others near the head and probably still others 
closer to the sacrum. There are also traces of what appear to be 
one or two caudal ribs. 
I find it impossible to determine exactly either the number or 
the form of the vertebrze, or the extent to which they are ossified. 
To Branchiosaurus Fritsch has attributed twenty presacral verte- 
bree, all of which possessed ribs except the most anterior. Prof. 
Cope thought that Amphidamus possessed probably thirteen. SBas- 
ing my judgment on the apparent length of a few centra, I think 
that the number will fall a little short of twenty. The neural 
spines must have been veryshort. Icannot determine the presence 
of distinct processes for the attachment of the ribs. The vertebral, 
column as a whole was slender, not broad as that of Branchio- 
Saurus. | 
The head, though about as broad as long, has its greatest breadth 
far behind, while the outlines converge with a gentle curve to the 
snout, which is thus not so broadly rounded as in many of the 
related forms. The bones of the head were probably ornamented 
with a raised network of lines, enclosing pits. Prof. Cope regarded 
the head as beingsquamous. Many of the sutures between the bones 
are indistinct. The premaxillaries are undoubtedly separate. They 
appear to have each a short and broad ascending process. Exte- 
rior to this lies the exterior nares, bounded behind by the large and 
separate nasals, which meet along the midline. Prof. Cope indi- 
cated with doubt a suture crossing the interorbital space between its 
anterior and middle thirds, and another between the middle and 
