in the Neighbourhood of Edinburgh. 207 
appeared no other resource left to this indefatigable naturalist, 
than‘to inquire whether, in other examples of recent or fossil fish 
allied to the Megalichthys, the larger or smaller teeth prevailed 
most in number. Ifthe larger or canine teeth should prove 
to be fewer in number, ‘and should have a more interior and 
anterior position among the bones of the mouth, he conceived 
that a great argument would be afforded for assimilating the spe- 
cimen of Burdiehouse to that of Leeds, whence their identity 
as one genus of fish, if not exactly established, would at least ‘be 
a reasonable presumption. 
Such a comparison was accordingly instituted, by which M. 
Acassiz came to the conclusion, that in the lesser number of 
larger or canine teeth, vr, in other words, in the far greater pro- 
portion of smaller teeth, the sauroid genus of Burdiehouse would 
be ultimately found to identify itself with that of Leeds, and 
that thus each animal would be referable to the Megalichthys. 
This anticipation has been remarkably confirmed in the sub- 
sequent discovery of part of a jaw, too late for M. Acassiz to see 
before he left England. It shews a larger tooth alternating with 
several of much smaller size. 'The relic (See Plate X. fig. 1) evi- 
dently belonged to a young animal, as it exhibits none of the im- 
mense and similarly striated teeth which have been found in a 
detached state. It, however, not only displays a larger tooth alter- 
nating with an excess of smaller ones, but likewise a difference 
of size between the two kinds,—so extraordinary, indeed, as to 
afford an illustration of the advantages which were to be derived 
from a comparison of isolated remains, with the connected ones 
of other animals, at least approaching to one common family. 
But I shall now advert to other investigations of comparison. 
Inthe recent and very remarkable sauroid fish conceived to 
bea living type of the Megalichthys,—the Lepidosteus spatula,— 
M. Acass1z observed phenomena nearly similar. He states that 
teeth of an inch long, alternate with small teeth which are nota 
dine in length. In ‘this species, he adds, the largest teeth are 
