1888. ] NEW YORK ACADEMY OF SCIENCES. 165 
-erystals from Japan, of clear quality ; one crystal being 5.94 
inches in diameter. 
Pror. J. S. NEWBERRY exhibited a jaw of Rhizodus, and pre- 
sented the following 
NOTE ON A NEW SPECIES OF RHIZODUS, FROM THE ST. LOUIS 
LIMESTONE AT ALTON, ILLINOIS. 
At the meeting of the Academy held May 2d, 1887, I ex- 
hibited jaws, teeth, and bones of a large ganoid fish discovered 
by Mr. William McAdams in the Mountain Limestone at Alton, 
Ill., and this is briefly described in the Transactions of the 
Academy, Vol. VI., p. 187, and named Celosteus ferox. I have 
now the pleasure of exhibiting to the society portions of the 
under jaw of an allied, but still larger, fish recently found by 
Mr. McAdams inthe same formation. This evidently represents 
a species of Rhizodus much like Rk. Hibberti, Ag., from the 
‘Carboniferous limestone of Scotland, of which the great laniary 
teeth are figured in most text-books on geology. The specimen 
now exhibited forms the anterior half of the dentary bone, which 
carries a large number of acute, conical, striated teeth, about half 
an inch in length, with three great laniary teeth, of which one is 
located near the symphysis, the others respectively four and a 
half and seven and a half inches further back. Of these the 
anterior only is perfect; this projects about two inches above 
the margin of the jaw, and is deeply implanted in its substance; 
the point is rounded off by wear, the sides are compressed, the 
margins acute, the base strongly fluted. It differs from the 
corresponding tooth in the Scotch species of Rhizodus in being 
more compressed and double-edged. This has suggested the 
specific name Rhizodus anceps, given to the species. 
The discovery of this specimen is of special interest, as proving 
the existence of an unmistakable species of Rhizodus in North 
America, contemporaneous with the great Scotch ganoid, and 
equally large. 
Several nominal species of Rhizodus have been described 
from the Carboniferous rocks of the United States, such as R. 
lancifer, N., R. quadratus, N., R. occidentalis, N., allfrom the 
Coal Measures of Ohioand Illinois, but it is by no means certain 
that any of these belong to the same genus with R. Hibderti, Ag. 
Sir William Dawson has described a fragment of a fish jaw 
from the Lower Carboniferous of Horton Bluff, Nova Scotia, 
under the name of Rhizodus Hardingi. 'This is apparently a 
true Rhizodus, and it is probable that the genus, strictly defined, 
will be found limited to the Lower Carboniferous rocks. 
