384 RAMSAY H. TRAQUAIR ON THE 
by a knowledge of the entire fish, no more compact or sharply defined group 
can be found in the whole range of ichthyology. In spite of the persistence of 
the notochord, the whole structure of these fishes evinces a high degree of 
specialisation, and the absence of connecting links with more generalised forms 
renders the systematic position of the family indeed hard to determine, though 
the structure of the internal skeleton seems to indicate that it appertains rather 
to the great Lepidosteoid series of Ganoids than to any other, One thing is 
certain, namely, that the Pycnodontide are widely separated from the 
Platysomidee by an assemblance of characters, upon which the anatomist is 
compelled to place very much greater weight than upon the mere external form 
of the scales.* 
The Suborder “ Lepidopleuride” of Professor Youne. 
We have already seen in the introduction to this paper that Professor 
Youne, unable to include the Platysomidz and Pycnodonts in one “family,” 
proposed, apparently as a sort of compromise, to institute the “suborder” of 
Lepidopleuride, 1 which both should be comprised, and which should be 
equivalent to the suborders Amiade, Lepidosteide, Crossopterygide, 
Lepidosteide, and Acanthodide, in Professor Hux LEy’s system. We may 
now briefly analyse Professor Youne’s definition of the “Lepidopleuride,” with 
the view of coming to some conclusion as to its validity as a suborder of 
Ganoids. 
He states that the Lepidopleuride are,— 
“Ganoids with heterocercal equilobate tails. Body rhomboidal, covered 
with rhombic scales articulated by strong ribs traversing their anterior margin 
internally. Dorsal fin equal to half the length of the trunk. Anal fin also with 
an elongate base. Ventrals when present small. Paired fins non-lobate. 
Branchiostegal rays not taking the forms of broad plates. Notochord 
persistent. Arches well ossified.” 
Some of these characters are obviously inapplicable to many prominent 
members of the assemblage of fishes which Professor YounG here proposes to 
* Besides Acassiz’s “ Poissons Fossiles,” the following works may be consulted in connection with 
the structure of the Pycnodontide :— 
Grey-Ecrrton, Sir Pam. ‘On the Affinities of Platysomus.” Qu. J. Geol. Soc. v. 1849. 
Waener, Dr A. “Beitriige zur Kenntniss der in den lithographischen Schiefern Bayerns abgela- 
gerten urweltlichen Fische.” Abh. Bayer. Ac. vi. 1850. 
Waaner, Dr A. “ Monographie der fossilen Fische aus den lithographischen Schiefern Bayerns,” — 
pt. i Abh, Bayer. Ac. ix. 1861. | 
THIOLLIERE, Victor, “ Poissons Fossiles du Bugey,” pt. i. Paris, 1854, 
Heoxet, J. J. “ Beitrige zur Kenntniss der fossilen Fische Oesterreichs.” Denkschr. Wien. Ac. 
xi, 1856. * 
(JuenstEDT, F, A. “ Handbuch der Petrefactenkunde,” second ed. Tiibingen, 1867. ] 
