AND ON THE CLASSIFICATION OF FISH. 505 
should be obliged to confess that the characters of this order are 
perfectly unknown, and the admission of many families among 
them would hence be more or less arbitrary. 
The chief points in Agassiz’s work, which is indisputably the 
most important ichthyological treatise of modern times, have 
been for some years before us. They have not hitherto been 
developed nor analysed by any philosopher in a proper manner. 
Wiegmann, in his report of 1835*, says of it, that the system, 
being based upon a single peculiarity of the organism, would 
give rise to the fear that it might prove rather an artificial than 
a natural system, and might occasion a doubt whether compara- 
tive anatomy would find as great an agreement among those com- 
prehended in the separate orders, as it might require from the 
orders of a natural system. But no facts are placed before us 
so as to enable us to judge. And it must be confessed, that 
means for such an analytical development of the increase in 
ichthyologic information which has lately been acquired have 
hitherto been wanting. 
I have been occupied for a long time with the anatomy of the 
Polypterus, and more lately of the Lepisosteus, endeavouring to 
ascertain the true characters of the order. I have succeeded, 
and I now think that I can positively prove,— 
1. That the Ganoids form a well-defined order, between the 
true osseous fishes and the Selacians. 
2. That Agassiz’s view of the position of the Sturgeons among 
the Ganoids is correct. 
3. That, on the other hand, the Sclerodermi, Gymnodontes, 
Loricarini, Siluroidet and Lophobranchii, do not belong to the 
Ganoids, but to the other osseous fishes. 
4. That there are unarmed and scaleless fishes, the families 
belonging to which gradually pass into one another, without 
losing the true Ganoid character. 
This is not the first time that Polypterus and Lepisosteus 
have been treated of. Geoffroy St. Hilaire has described the 
intestines of the Polypterus which he discovered ; we have also 
papers on its osteology both from the same author, and more 
detailed ones from Agassiz. Agassiz has taught us the osteo- 
logical peculiarities of Lepisosteus; Cuvier, Valentin and Van 
der Hoeven have examined its intestinal system. Although these 
communications are valuable towards our anatomical knowledge 
* Archiv f. Naturgesch, 1 Jahyg. ii. p. 258, 
