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ARTICLE XIX. 
Further Remarks on the Structure of the Ganoidei. 
By J. MUuuer. 
[Read before the Berlin Academy of Sciences on the 12th of March, 1846.] 
In my memoir on the structure of the Ganoids, I made known 
some important internal peculiarities of the Ganoids, and showed 
that these animals, which resemble the osseous fishes in having 
an operculum, differ from them in possessing a muscular layer 
on the arterial trunk and numerous rows of valves within it, as 
also in possessing a chiasma of the optic nerves, whilst the os- 
seous fishes have only two valves at the arterial orifice of the 
ventricle and are deficient in the prolongation of the muscular 
substance of the heart upon the arterial trunk; moreover, their 
optic nerves proceed simply across one another without inter- 
mixing. The Ganoids differ in these particulars from the os- 
seous fishes, but agree perfectly with the Selachii (the Sharks, 
Rays and Chimere).. In addition to these general and absolute 
internal characters of the Ganoids, I mentioned others, which 
are also peculiar to them, inasmuch as they are never observed 
in true osseous fishes, but which do not however occur in all the 
Ganoids. In these, among other things, I placed the existence 
of a respiratory opercular gill and the spiral valve in the intes- 
tinal canal. The former is present in the Sturgeons, Scaphi- 
rhynchus aud Lepisosteus, but is wanting in Polypterus and Spa- 
tularia; the latter is seen in the Sturgeons, Scaphirhynchus, 
Spatularia and Polypterus, whilst it appears to be wanting in 
Lepisosteus. The absence of the omental fissure in the Ganoids 
had not then been generally observed. The object of the present 
communication is to show that the absolute or constant general 
characters of the Ganoids are more numerous, and that many of 
those characters which are absent in osseous fishes, but which 
did not appear to be peculiar to all the Ganoids, are in fact 
universal. 
Since my last treatise, the materials for the anatomy of the 
Ganoids have considerably increased. Dr. Roemer has sent me 
a Spatularia and a considerable number of specimens of the 
long-snouted Lepisosteus, from North America, in spirit. 
