On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 347 
referred to the genus Leptacanthus, viz., L. occidentalis, with the remark that there 
seems “little probability that they are generically identical with those from the 
Oolite.” The general form is similar, but the striated or obscure and confusedly costate 
surface of the typical Leptacanthi must have given them an aspect widely different 
from that of these spines so uniformly and regularly ribbed throughout. He 
further points out, that in no instance have teeth been found in the J urassic and 
Carboniferous rocks, which are common to both and might have belonged to the 
fish bearing the spines Leptacanthus. The close resemblance of these spines with 
the slender and compressed forms which have been included in Ctenacanthus, such 
as C. distans, M‘Coy, and C. gracillimus, N. and W., is also remarked, and a sugges- 
tion made that these slender and flattened species of Ctenacanthus and the Carbon- 
iferous Leptacanthus should be combined to form a new genus separate alike 
from Ctenacanthus and Leptacanthus. 
This suggestion was to some extent carried out by Messrs. Orestes St. John and 
A. H. Worthen, in the sixth volume of the “Geol. Survey of Illinois,” p. 432, by the 
formation of the genus Acondylacanthus, with two species from the Kinderhook 
fish-bed and the Keokuk limestone respectively, viz.:—A. gracilis and A. equi- 
costatus. This genus is also considered to embrace the following described species, 
all of which pertain to the Carboniferous period: Leptacanthus junceus, M‘Coy, 
L. jenkinsoni, M‘Coy, L. occidentalis, N. and W., and Cladodus tenwistriatus, 
Romanowsky. The last named, though evidently a spine of Leptacanthus, was 
considered by Col. Romanowsky to be associated specifically with the teeth of 
Cladodus, from the fact that the two were found associated with each other. 
The rearrangement as suggested by St. John and Worthen appears in every 
sense preferable and will be followed in the present instance. 
Acondylacanthus colei, Davis. 
(PL, SIL, ities, 7 g Tl, OIL al, te, I) 
Fin-spine, gently arched and gradually tapering toa fine point. Base imperfect ; 
length preserved 5°5 inches, greatest diameter at base ‘35 inch, which steadily 
diminishes towards the apex. Transverse section rounded anteriorly and laterally, 
posterior flattened or depressed; internal cavity, large and round. Sides orna- 
mented with a number, about twelve, of delicate, enamelled coste, extending 
longitudinally, parallel with the anterior surface, towards the base they increase by 
bifurcation; the intermediate hollows are smooth and narrow. ‘The anterior 
margin is rounded, the longitudinal strize of the sides are continued anteriorly ; 
there is no median keel. Posterior face, broad, somewhat deeply channeled. 
Latere-posterior angles sharply defined, bearing on each side a row of obtusely 
pointed, widely separated denticles. 
The spines comprised in this species have been classed with those of Acondyla- 
