198 PALEOZOIC FISHES OF NORTH AMERICA. 
the type species of Physonemus (Ph arcuatus, McCoy), that they should not 
be included in the same genus. I would therefore propose for the former 
a new generic name and briefly define it as follows: 
STETHACANTHUS, nov. gen. 
Pectoral spines of medium or large size, unsymmetrical (rights and 
lefts), broadly faleate in outline, the conical summit compressed, with ante- 
rior and posterior margins rounded. Below the solid summit the posterior 
margin is opened by a deep sulcus, of which the walls, of unequal thickness, 
terminate posteriorly in thin and fragile edges; anterior border gently con- 
cave, about one-third its length from the base rising into a strong, often 
tumid, shoulder: basal portion narrow and compressed, terminating in a car- 
tilaginous condyle for articulation. In life the posterior sulcus was occu- 
pied by the base of the pectoral fin. Type species St. Altonensis, St. J. & 
W., sp. 
For the species found at Berea, Ohio, I propose the name Stethacanthus 
tumidus ; giving as its specitic characters those of the genus with the follow- 
ing additions: Spine large, massive, laterally compressed, upper half trian- 
gular in outline, anterior shoulder broad, tumid, overhanging, and some- 
what bilobed. 
Since the above notes were written I have received from Alton, IIl., a 
number of specimens of Stethacanthus Altonensis which show the want of sym- 
metry noticed in those from Berea. One of these specimens is of extraor- 
dinary size and of unusual breadth, so I have thought best to give figures of 
both sides of it in order to show with its dimensions the want of symmetry, 
one of the sides being as usual considerably shorter than the other." 
LABODUS MARGINATUS, 0. Sp. 
Plate XIX, Fig. 9. 
The little tooth represented by the figure cited above is one of several 
received from Greencastle, Ind., where they were obtained from the Saint 
Louis limestone. They evidently belong to a group of palate teeth of which 
many have been found in the Lower Carboniferous limestone at Armagh, 
'See pl. XXIV, figs. 1, 2. 
