THE DEVONIAN ROCKS OF CANADA. 107 
and those of the nearly related Canadian form. The European species seems, however, to 
have attained to a much larger size than the Canadian, for Agassiz says that some of the 
plates of B. ornata are as much as six inches in length, whereas the largest of the 
P. Canadensis yet found are little more than three inches and a quarter in their maximum 
diameter. 
ACANTHODES MITCHELLI ? Egerton. 
Acanthodes Mitchelli, Egerton, 1860. Memoirs of the Géological Survey of the United 
Kingdom. Figures and Descriptions of British Organic Remains, 
Decade X. p. 57, Plate VI. Figs. 1 and 2. 
Maximum length about an inch and three-quarters ; outline subfusiform, but much 
deeper on the ventral than on the dorsal aspect, the back being apparently almost straight. 
The deepest part of the body is midway between the pectoral and ventral fins, where the 
largest specimen (which, however, seems to be abnormally compressed and spread out in 
the ventral region) measures five lines. Head about one-fifth of the entire length of the 
body, including the caudal fin. Lateral line distinct. Scales minute, rhomboidal, imbri- 
cating and smooth when examined with a lens. Fin spines very lightly recurved, with 
two deep, longitudinal grooves, the anal being placed slightly in advance of the single 
dorsal. 
Twelve specimens of this little fish were collected by Mr. A. H. Foord in 1881, the 
smallest of which is half an inch in length and the largest an inch and three-quarters. 
These seem to agree with Sir Philip Egertou’s description and figures of A. Mitchelli in so 
many particulars that they are here referred to that species, though not without much 
doubt. In the figures which accompany the original description of A. Mitchelli, the outer 
surface of the scales is indeed represented as densely granulose or minutely tuberculated, 
but Mr. J. Powrie asserts that this representation is erroneous, and that “ better speci- 
mens prove them to have been perfectly smooth.” The largest specimen collected by 
Mr. Foord is about one-third less in its greatest length than the types of A. Mitchelli, 
though this slight difference in size alone can scarcely be considered as affording a means 
of specific distinction. Still, the Canadian specimens may prove to be quite distinct from 
A. Mitchelli, and in that case, the writer would venture to suggest for them the name 
A. affinis. 
ACANTHODES CONCINNUS, N. Sp. 
(Plate X. Figs. 1 and 1a.) 
Length of the largest specimen collected about six inches, greatest height of the same 
about one inch; outline narrowly fusiform (though all the specimens are so much crushed 
and distorted that the exact shape is somewhat uncertain), head about one-sixth the total 
length. Fin spines ornamented with about four longitudinal grooves, rather short and 
slender in proportion to the size of the body; anal spine situated below and slightly in 
advance of the dorsal; pectoral spines stout, longer than any of the rest; ventral spines 
small. Scales rhomboidal, scarcely imbricating, and so minute as to be quite invisible to 
