FISHES OF THE CARBONIFEROUS SYSTEM. 201 
Crenacantuus Lirront, n. sp. 
Plate XXV, Fig. 3. 
Spines twelve to fifteen inches in length by three centimeters in width 
at the base of the ornamentation; form nearly straight, with a slight back- 
ward curvature; laterally compressed; section elliptical; anterior margin 
rounded, posterior somewhat flattened; ornamented portion occupied by 
many relatively narrow, closely crowded, longitudinal ridges, of which those 
on the anterior margin are broadest; on these are closely set, prominent, 
transverse, vertically compressed, lenticular, enameled tubercles; unorna- 
mented base very long, extending four inches or more beyond the lowest 
point of the enameled surface, outline conical, pointed, surface smooth or 
finely striated longitudinally ; sides flattened; posterior margin open to tip. 
Above the base the posterior opening is narrow and reaches to the middle 
of the spine. 
Only fragments of this remarkable spine have yet been obtained. A 
complete base with a small portion of the enameled surface is shown in 
Fig. 3, and it will be seen that this base is of remarkable length and smooth- 
ness. The ornamentation is crowded, as regards both the costa and the 
tubercles; both are contiguous, with no open space between them; the tu- 
bercles are transversely lenticular, much broader than high, smooth and 
polished. They are sufficiently prominent to give a rasp-like roughness to 
the surface. 
The summit of the spine is yet unknown, and nothing can now be said 
in reference to the posterior armature. 
Comparing this with other spines of the genus it will be seen to be 
quite distinct from any heretofore described. The form must have been un- 
usually graceful, and the ornamentation is more elaborate than in any other 
species known to me. The tuberculation of the surface is different from the 
ordinary pectination formed by transverse, sheath-like ridges on the coste, 
but consists of distinct, bead-like tubercles closely set along the ridges, and 
from their prominence and distinctness liable to be broken off, leaving a 
series of flattened spaces upon which they rested. This ornamentation is 
