108 WHITEAVES ON FOSSIL FISHES FROM 
. the naked eye. When viewed under the microscope, they are seen to be marked with 
from seven to eight acute and for the most part simple, longitudinal striæ, which, how- 
ever, occasionally bifurcate. In some specimens, the striæ upon the scales seem to be 
nearly parallel, but in others they radiate from the posterior angle of the scale. Tail 
distinctly heterocercal, the upper lobe projecting considerably beyond the lower. 
About a dozen specimens of this species and a few fragments were collected by Mr. 
Foord in 1881. These are all very much distorted, as so often happens to Acanthodians, 
and the fin spines are in no case all preserved in their-normal position, so that it is quite 
impossible to be sure whether there was originally one dorsal fin or two. In the most 
perfect examples there seems to be only six fin spines, and if there were two dorsals there 
ought to be seven. The scales are often very well preserved, but the head is nearly 
always broken off. The species appears to differ from A. Mitchelli, and from all the other 
Scotch or European forms of the genus, by its much greater size and by the peculiar 
sculpture of its scales. It was at one time supposed by the writer to be a Diplacanthus 
allied to the D. longispinosus of Agassiz, whose scales are similarly sculptured, but it appears 
to have had only one dorsal fin. 
PHANEROPLEURON CURTUM, Whiteaves. 
Plate X. Figs. 2, 2a, b, c, d, e. 
Phaneropleuron curtum, Whiteaves, 1880. Canadian Naturalist and Geologist, New Series, 
Vol. X. p. 29! 
Maximum length about fifteen inches; greatest height or depth of the same specimen, 
six inches and a half. All the specimens known to the writer, however, are crushed quite 
flat laterally, and this, of course, makes the proportionate height or depth look greater than 
it originally was. General outline, exclusive of the fin rays, varying in different indivi- 
duals from rather broadly ovate to fusiform, but at the tail end the body always narrowed 
to a slender and acute point. Head rather small in proportion to the size of the body, 
about one-fourth or one-fifth the entire length. Cranial plates not very thick, polygonal 
and more or less elongated longitudinally ; very similar in outline to those of Dipterus, 
as figured by Hugh Miller in the “ Footprints of the Creator.” ’ Outer surface of the 
cranial plates apparently smooth to the naked eye, though when examined with a lens, it 
seems to be minutely pitted and irregularly grooved ; inner surface of, at least, some of the 
cranial plates marked with radiating grooves and ridges, which are plainly visible to the 
naked eye. Scales thin, cycloid, imbricating, their exposed surfaces concentrically striated 
and marked also with exceedingly minute radiating lines, which latter are only visible 
under a somewhat powerful lens. In a single specimen of a small fragment of the body, 
the lateral line is very distinctly shown. 
Dorsal fin apparently single, very long and large, commencing anteriorly in a line 
with the posterior termination of the head, but little raised as far as the midlength, after 
which it suddenly becomes strongly elevated and continues so for the rest of its length, 
and is finally confluent with the upper lobe of the caudal. Height of the posterior por- 

1 8rd ed., London, 1850, p. 61. 
