FISHES OF THE DEVONIAN AGE. 37 
figured will doubtless be looked upon with interest, and will stimulate the 
search for more remains of what has till recently been an entirely unknown 
Devonian fish. 
Order ELASMOBRANCHII. 
Genus MACHA.RACANTHUS, Newb. 
Spines often of large size, curved, ancipital, unsymmetrical (dextral 
and sinistral); edges and point generally acute; base somewhat narrowed, 
with a rough and irregular extremity ; central cavity reaching nearly to the 
apex; external surface covered with a thin coating of enamel, in some spe- 
cies smooth, in others punctate and longitudinally striated; microscopic 
structure that of dense, ivory-like bone. 
These spines are very characteristic of the horizon of the Corniferous 
limestone, having been found at this level in Indiana, various localities in 
Ohio, in New York, and at Gaspé, Canada. Though representing some 
anomalous characters, among which the most remarkable is their want of 
symmetry (being rights and lefts), it is hardly possible they can be any- 
thing else than the defensive spines of fishes. Their dense, bony structure, 
enameled surface, and rough irregular bases would seem to prove that, like 
the fin spines of many Sharks and Rays, they had been implanted in the 
integuments without articulation. Probably they were the first rays of the 
pectoral fins, which would account for their being in pairs. In that case it 
might be expected that the bases would exhibit some marks of their artie- 
ulation to the pectoral arch; but as the fishes which bore them were 
undoubtedly cartilaginous, the insertion of pectoral spines—supposing they 
possessed them—would naturally somewhat resemble that of the dorsal 
spines. Many bony fishes, as Arius, ete., bear formidable dorsal and pec- 
toral spines, but these always exhibit some indications of an articulation at 
their proximal extremities. In the Sharks, Chimeras, and Rays, however, the 
dorsal spines are simply implanted in the integuments of the back, and each 
spine has a roughened and attenuated base, which is surrounded by a larger 
or smaller mass of cartilage. 
