552 THE AMERICAN NATURALIST. < [VOL XXXII. 
having the anterior margin uniformly curved, show a slight 
angulation at the region of maximum width, in that the spine 
tapers gradually from this point in both directions, distally 
and proximally. 
Obviously these spines, differing as markedly as they do 
from the majority of Palaeozoic ichthyodorulites, cannot be 
included under any known genus or species. We therefore 
propose the new genus Phlyctenacanthus for their reception, 
and have pleasure in naming the species P. ¢e//eri in honor of 
the veteran and indefatigable collector, Mr. Edgar E. Teller. 
Regarding their affinities, we can only suggest that they may 
have pertained to Paleomylus. Their large size precludes an 
association with either Rhynchodus or Ptyctodus; and Cladodus, 
the only other Elasmobranch known to occur in the Wisconsin 
Hamilton, was in all probability a spineless shark. On the 
supposition that these were the spines of Pryctodus ferox, then 
we ought by good rights to have found similar fossils in the 
State Quarry fish bed, where there is such a wonderful concen- 
tration of Ptyctodus remains. But such spines as have been 
recovered from the Iowa locality are very different from 
Phlyctenacanthus. The latter are thus definitely excluded 
from all known genera occurring at Milwaukee, except Palzo- 
mylus. But as we know nothing, for instance, of the dentition 
with which Heteracanthus politus was associated, so, too, there 
is as much likelihood of P. ¢e//ert belonging to some unknown 
Elasmobranch genus as to Palzomylus. But as to the relative 
probability of one of these “genera ” of Milwaukee ichthyo- 
dorulites belonging to the Ptyctodontide, the evidence of the 
tuberculated Russian fin-spines would go to show that 
Phlyctenacanthus is the likelier of the two to have its position 
established here. 
(2) Belemnacanthus giganteus gen. et sp. nov. (Fig. 50). — 
This is the last form to claim our attention, and we notice it 
here more on account of its accompanying Ptyctodont remains 
in the Eifel Devonian than with the intention of suggesting 
possible Chimzeroid affinities. In fact, we are inclined to sus- 
pect that it may have been of Ostracoderm rather than of Elas- 
mobranch nature. But without entering into the question of its 
