630 PROCEFDINGS OF THE GEOLOGICAL SOCIETY, [June 22, 
and articulating lengthwise by notches and points. The fin-rays, 
which occupy more than half the width of the entire lobe, are rather 
delicate, jointed, and bifurcated once or twice at the extremities. 
The rays are longest and are much inclined on the lobes, and be- 
come shorter and less inclined in the axis of the fork. 
Perhaps the most curious feature in this interesting fish is found 
in the character and mode of arrangement of the more or less bony 
plates and rods, regarded by Germar as composing an internal 
“bony skeleton;” and, indeed, in the general disposition of the com- 
ponent parts there is a strong resemblance to such. On examin- 
ing them in detail, however, there are one or two anomalous features 
which render it difficult to work out the homologies of the bones; 
and the discrepancies are of a nature to raise the questions, Do, in- 
deed, all these bones really belong to an endo-skeleton? and may 
they not in part belong-to an exo-skeleton? Before, however, en- 
tering on these points it will be better to describe the form and ar- 
rangement of these peculiar plates and rods. And for the sake of 
avoiding circumlocution, and to simplify the description, we shall 
give to the various parts distinct names, referring only occasionally 
to those in general use, for the purpose of pointing out resemblances. 
The plates and rods are arranged in transverse series, of which 
there are twenty-seven or twenty-eight, extending from the occiput 
to the root of the tail, reminding one much of the disposition of the 
transverse flakes of muscle observed on the sides of the body of a 
fish when the skin has been removed. ‘These transverse series of 
plates and rods are, for the most part, placed a little asunder, but 
are at some points in contact, and occasionally seem as if imbricated. 
They are in contact along the longitudinal middle line, which corre- 
sponds to the usual lateral line or the line of the vertebral column. 
Here there is a chain of lozenge-shaped plates or areas (2) with their 
angles placed lengthwise and transversely. In the centre of each there 
is an elongated rounded ridge (fig. 2, h') placed longitudinally; these 
ridges resemble the mucus-tubes of the lateral line of certain fishes. 
These lozenge-shaped areas or plates measure about ~5 inch across. 
From either side of each of them there extends a longitudinal trans- 
versely elongated plate (figs..1, 2, ) inclined backwards, the largest 
of which measures about 3 inch in length; these, which we shall call 
the lateral plates, are expanded and bifurcated (g’) in the direction of 
the length of the fish at their inner extremities, and thus embrace, as 
it were, the lozenge-formed areas or plates bearing the ridges already 
described ; or perhaps this arrangement would be better described 
by stating that the forks of the opposed plates, meeting on the me- 
dian line, form the lozenge-shaped areas or plates, to which they 
give an elevated border. The lateral plates have a boss-like en- 
largement at the point of bifurcation ; here the plates are narrowest ; 
hence they widen gradually for some distance, and then, turning 
backwards, taper to the termination. The margins are abruptly 
defined, and are slightly elevated into narrow ridges, which die out 
towards the outer margin. The bifurcations of the adjacent plates 
are in contact ; and so are the outer terminations. But for the rest, 
