PLATE LVI. 
Notwithstanding the example of the great Linnaeus, there is a ra- 
dical defect in presuming, that the presence or absence of any par- 
ticular fin, can constitute an unerring specifical distinction of the 
different fishes of this genus. Nature has herself afforded other 
characters, that are equally perspicuous, and more constant, or at 
least less liable to accident. Sometimes Linnaeus has paid a cursory 
attention to those characters, but he does not attend sufficiently to 
them. The fallacy of the Linncean specific characters, will be at 
once seen for instance in the species Acus: should this be acci- 
dentally bereft of the anal fin it becomes Pdagicus ; and it is only 
by regarding its secondary character with caution, that the error can 
be detected. Again, if both the pectoral and anal fin be destroyed, 
What criterion have we to distinguish it from JEquoreus ? Ophidion 
affords another example of the same nature : when recent, the body 
is round and smooth, but when dry, appears llightly hexagonal, and 
in this state, scarcely differs from the Linnsean species Bar'barus ; the 
Pectoral fins are then the principal distinction, and if these be broken 
°ff, the Opidion will correspond with the character of that species *. 
* In treating of any genera less ambiguous than the present, Limneus could not bo 
Considered blameable for adopting characters that might render imperfect specimens of 
the species he describes liable to misconception. But when we consider the confusion 
likely to prevail among the I. inn .can Si/ngnuthi, and their synonyms, in consequence, wc 
cannot avoid expressing a wish that he had attended more closely to other collateral charac- 
ters, He does regard the shape of the body, but this is not sufficient, flic exact struc- 
ture of the snout, if taken into consideration, would have greatly assisted in determining 
the respective species. 
The fins in all these fishes are small and delicate, and therefore apt to he frequently mu- 
tilated, and in dried specimens especially. In the figures given by old writers, we seldom 
thid the fins correctly drawn, the fault arising perhaps from this cause, rather than lrotn the 
