CLASSIFICATION OF DEVONIAN FISHES 445 
The characters of five of the six families which compose this 
suborder have been given, incidentally, in the preceding pages, but 
the table contains another family whose collocation with the rest 
requires justification. 
This is the family of the PHANEROPLEURINI, which I have esta- 
blished to contain the singular genus Phaneropleuron, described at 
length in this Decade (p. 505) and figured in Plate III. The general 
character of this fish, its thin cycloid scales, the mode of termi- 
nation of its caudal extremity, and its remarkable, very acutely 
lobate, ventral fins, lead me to entertain very little doubt that its 
right place is among the Crossopterygide, and in the neighbour- 
hood of the Glyptodipterini and Ccelacanthini, though I have not 
yet been able to obtain a very good view of its jugular plates. But 
the very long, single, dorsal fin, the great length and acute lobation 
of the ventral fins, which seem to have been longer than the pectorals 
and the complete ossification of the costal elements and neural arches 
throughout the vertebral column, separate Phaneropleuron alike 
from the Glyptodipterini and the Ccelacanthini. From the Cteno- 
dodipterini it is separated not only by these characters, but by its 
dentition. Under these circumstances the only course seems to be 
to regard it as the type of a distinct family. 
The group of Crossopterygidex, as thus established, appears to 
me to have many remarkable and interesting zoological and 
paleontological relations. Of the six families which compose it, four 
are not only Palzozoic, but are, some exclusively and all chiefly, 
confined to rocks of Devonian age,—an epoch in which, so far as 
our present knowledge goes, no fish belonging to the suborders 
of the Amiadz or Lepidosteide (unless Cheirolepis be one of the 
latter) makes its appearance. Rapidly diminishing in number, the 
Crossopterygidze seem to have had several representatives during 
the Carboniferous epoch, but after this period (unless Ceratodus be a 
Ctenododipterine) they are continued through the Mesozoic age only 
by a thin, though continuous, line of Coelacanthini, and terminate, at 
the present day, in the two or three known species of the single 
genus Polypterus. Polypterus, however, is clearly related to the 
rhombiferous Crossopterygians, or in other words, to exactly that 
group of whose existence we have no knowledge in any Mesozoic, or 
Tertiary, formation; while the Ctenododipterini and Ccelacanthini, 
which depart most widely from Polypterus, are those which con- 
tinue the line of the Crossopterygide from the Paleozoic to the 
end of the Mesozoic epoch. Thus both ends of the Crossopterygian 
series appear, if I may use the expression, to be cut off from the 
