FISHES OF THE CARBONIFEROUS SYSTEM. 197 
tively to which of these, but since we have several examples of pectoral 
spines among the ancient sharks (Gyracanthus and Macheracanthus) and 
innumerable examples among living fishes, while ventral spines are almost 
unknown, we may infer that they were pectoral spines. 
All the specimens referred to were obtained by Dr. Clark from a pyri- 
tous layer resting upon the Berea grit, where they are often replaced by 
pyrite, and for the most part imperfectly preserved. One specimen, how- 
ever, found in the fine argillaceous shale which overlies the Berea orit, 
gives the complete outline of the spine, and what is of special interest, the 
fin that was attached to it is represented by numerous well-preserved rays 
lying closely approximated in their natural positions. The spine, which 
here has its complete form, has evidently suffered no abrasion, as is proved 
by the preservation of the fin itself; and as it is without ornamentation, we 
are compelled to believe that it never bore any tubercles. The base shows 
the outline of what seems to be a spheroidal head that fitted into the socket 
of an articulation. The fin rays are apparently jointed towards the base, 
dividing above into thread lines, which must have been at least partially 
ossified, since many of them are continuous to their extremities, which form 
a curve that must be nearly the outline of the fin. 
In the associated beds of the Waverly group, as well as in the Berea 
grit, a large number of dorsal spines have been found, among which are 
three species of Clenacanthus, and with these in several instances rays, that 
probably belonged to the dorsal fins of which the spines formed the de- 
fenses. These fin rays are six to eight inches in length by a quarter of an 
inch in diameter at the base, tapering to an acute point; they are smooth 
and without articulation, but that they were at least partly osseous is proved 
by the perfection of their preservation. 
At Vanceburgh, Ky., in a black shale of the Waverly group, among 
many other fish remains described in the Paleontology of Ohio, the tail of 
a large shark was found in which the fin rays of the lower lobe were dis- 
tinctly preserved and had evidently been ossified. This specimen is now 
in the State Museum at Frankfort, Ky. 
From the above description of the group of spines typified by Physone- 
mus Altonensis, St. J. & W., it will be seen that they are so different from 
