558 MULLER ON THE STRUCTURE OF THE GANOIDS. 
as on the shields of some Ostracia. However, I have shown, 
in my previous treatise, that the Ostracia are osseous fishes. 
As regards the position of Amia in the Ganoid system, it may 
even now be remarked, that it cannot be referred either to the 
family of the Lepidoséeini nor to the Polypterini: for it is sepa- 
rated from the former by the absence of fulcra on the fins, from 
the latter by the absence of that formation of the fin which is 
peculiar to Polypterus—the polyptery of the dorsal fin. I re- 
gard Amia as the living representative of a peculiar family of 
Ganoids, genera analogous to which in form, formation of fins, 
soft scales and osseous vertebral column, may be readily recog- 
nised in the fossil Megalus, Leptolepis, Thrissops and their allies, 
in short in the Ganoidei holostei, which are unprovided with 
fulcra to the fins. The difference between the Amide and the 
Celacanthi as families of the Ganoids is sufficiently shown in 
what has been stated above on the unossified state of the verte- 
bral body in Undina; notwithstanding, fulcra have also been 
observed on the fins of Macropoma. 'The Lepidosteini are very 
numerous in the fossil Ganoids with double rows of fulcra to 
the fins (Lepidotus and its allies): the Polypterini have no repre- 
sentatives among fossils. 
Finally, it deserves to be considered, what prospect there may . 
be of the number of recent Ganoids being increased by further 
anatomical examination of the genera as to the characters which 
I have propesed. Ganoids can hardly be concealed among sea- 
fishes, and if any should exist, they should be sought for 
among the few genera of river-fisk with abdominal ventral fins 
which have not yet been examined. North America, and the 
fauna of Ohio (Rafinesque ichthyologia Ohiensis), would deserve 
especial attention. Among some forms which have not yet 
been again found, Sarchirus vittatus of Rafinesque, I. Acad. 
Philad. i. 418, tab. xvii. fig. 2, appears worthy of attention, on 
account of its form. I placed this fish provisionally among the 
Scomberesoces ; its position must yet be decided by an exami- 
nation ofthe os hyoides and the valves of the heart, &c. 
