524 MULLER ON THE STRUCTURE OF THE GANOIDS, 
testines* ; there is no spiral valve in the intestine. The swim- 
ming-bladder is cellular, and contains trabecule carnee between 
the cell divisions +: it opens by a long slit into the upper wall 
of the throat. The ¢rabecule carnee are not the cause of the 
cellular structure, as usually supposed ; on the contrary, I find 
that the arrangement of the fleshy fibres is caused by the cel- 
lular structure of the walls; for the muscular structure of the 
fibres between the cellular spaces entirely ceases at a certain 
point, and the areas lying between them do not possess any sub- 
sequent evidence of muscular structure in their dividing lines 
(fibres) t. The termination of the muscular structure on the 
fibres, in those which possess it, is very distinctly perceptible. 
This view is opposed by the cellular structure of the swimming- 
bladder in other fishes, in which no ¢rabecule carnee occur. 
The same occurs in the Erythrinus and some Siluroidei, and 
which have been elsewhere described. Amia calva, which I have 
recently examined on this point, should also be included. 
Po.ypreRvs.—Its upper jaw is not divided into pieces, the 
vomer is simple, the lower jaw has the ordinary number of osse- 
ous pieces found in fishes, and the whole skull differs altogether 
but little from that of other fishes; at the angle of the mouth it 
possesses a labial cartilage supporting the upper and lower lips. 
The vertebrze on each surface are furnished with excavated facets, 
but no articular processes or sockets§. The opercular gill is 
wanting, no pseudo-branchia ever occurs, but they are provided 
with a blowing-hole on each side covered with an osseous valve. 
The fourth gill is composed of one leaf, and there is no fissure 
behind it; the ossa pharyngea inferiora are also wanting. ‘The 
gill-membrane is cleft in the middle, and instead of any rays to 
the gill-membrane, there are merely a few osseous plates on each 
side. Along the back there is a perfect row of separate fins, 
each of which consists of a prickle and a fin-feather of articu- 
lated rays attached to its posterior surface, no other example of 
® Valentin says the portal appendages are situated at the junction of the 
duodenum with the small intestine (Repert. 1840, p. 397). In this case the 
pyloric tube of the stomach is called the duodenum. 
+ See Valentin, /. c. 392. V. d. Hoeven, Mull. Archiv, 1841, p. 224. 
+ In the specimens from the Paris collection which I examined the intestines 
had been removed from the abdomen, but a small portion of the swimming- 
bladder was left behind, which was sufficient for the examination of the cells. 
§ On the osteology of Polypterus, see Geoffroy St. Hilaire’s Description de 
VEgypte. Agassiz, /. ¢. ii. 2, 32, and Miiller in Jahresbericht Archiv, 1843, 
p- ccxl. 
