from the Shales of the Northumberland Coal-field. 359 
must be taken to qualify it. They are,—‘ Mais les dents sont si 
excessivement petites qu'il est trés-rare de pouvoir les distin- 
guer.” From this it is pretty evident that this distinguished 
naturalist knew very little about the matter. Succeeding 
writers, however, appear to have rested satisfied with this 
description. Mr. Binney, indeed, so long ago as 1841* figured 
the jaw of Paleoniscus Egertoni, showing a row of large, co- 
nical, sharp-pointed teeth, as well as a few of the small ex- 
ternal ones. He says that the jaw is “armed with sharp 
conical teeth of a nearly uniform size, inclining from the 
front.”’ This communication, however, has been unfortunately 
overlooked. 
The teeth of these jaws are not “en brosse,” neither are 
they of that feeble “ villiform” structure so much insisted on 
of late. They are disposed in two-distinct rows, one within 
the other, much in the same fashion as in Megalichthys and 
Rhizodopsis, but still much more like that which obtains in 
Pygopterus, in which the teeth are likewise arranged in two 
rows—one being of large laniary teeth, the other of small 
external ones, And, according to M. Agassiz, they do not in ° 
this genus form “ une brosse ou rape comme les dents du Po- 
lyterus.” 'The inner row in Palewoniscus (Pl. XV. figs. 3, 4, 5) 
is composed of a few comparatively large, curved, sharp-pointed 
conical teeth, which are placed at some little distance apart 
from each other. In the outer row the teeth are numerous, 
small, conical, and pointed, occasionally crowded, and in some 
species apparently not quite in regular order. | 
It is this outer row of comparatively small teeth that appears 
to have been seen and described by M. Agassiz, the inner row 
of laniary teeth having escaped his observation. Nor is it any 
wonder that such a matter of detail should have been over- 
looked by this naturalist; and, indeed, many such omissions 
are found in the great work alluded to. But when we con- 
sider the novelty and vastness of the matter before him, and 
especially that the bent of his mind was directed mainly to the 
larger problems of his subject, the only marvel is that such 
_ blunders are not more numerous. The laniary teeth are 
very frequently concealed in the matrix; and when the jaw 
is im its natural position, they are liable to be obscured by 
the external row, which stands up on an elevated ridge of the 
alveolar margin. 
The laniary teeth vary in number in the different species, 
and probably, in a limited degree, even in the same species : 
but this is difficult to determine; for it rarely happens that the 
_* Trans. Manchester Geol. Soe. vol. i. p. 167, pl. 5. fig. 12 (1841). 
