STRUCTURE AND AFFINITIES OF THE PLATYSOMIDA. 347 
tion of the Ganoids,” has accepted the Lepidopleuride, but with this modifica- 
tion that the genus Tetragonolepis of Bronn and EGErrTon, rejected by Dr 
Youne as being a true Lepidosteid form, is introduced as the type of the family 
“ Pleurolepide,” while the four families ito which the last-named author 
divided the paleeozoic heterocercal forms are merged into one,—that of the 
“ Platysom.” To the Pleurolepide, Dr LUTKEN conceives it possible that the 
imperfectly known Cleithrolepis of EGERTON may belong; while of Hurynotus 
he says that perhaps it is “‘a palzeozoic, heterocercal Stylodont or Spheerodont.” 
Likewise, in Professor Vicror Carus’s “ Handbuch der Zoologie,’* the Lepido- 
pleuridz are accepted and divided into the three families of Platysomide, 
Pleurolepide, and Pycnodontide, Eurynotus being, however, retained in the first. 
More recently, however, Professor E. D. Copet has reverted to the plan of 
placing Platysomus in one family with Dapedius and Tetragonolepis, for which 
he adopts the term “ Dapediide ” in place of WacneEr’s “ Stylodontes.” Hury- 
notus, however, he places in the family “ Lepidotide,” along with Lepzdotus, 
Pholidophorus, &c., a group which he renders still more heterogeneous by the 
addition to it of Amblypterus, Palwoniscus, and Cosmolepis. Nothing is said 
regarding Amphicentrum and Mesolepis, and on the whole this classification 
can hardly be considered as an improvement on that of Professor Youne, of 
whose work the author seems to take no cognisance. 
That the paleozoic forms enumerated on the first page of this memoir 
constitute a connected series is undeniable, and considering the small number 
of genera, it seems convenient to follow Dr LUTKEN and Professor Carus in 
uniting them in one family group. I have already expressed my opinion { that 
these fishes have little in common with the Pycnodonts, while they are 
intimately allied to the Paleeoniscide, and that the suborder ‘“ Lepidopleuride ” 
must be abandoned,—to follow up this idea more in detail is the object of the 
present paper. I shall therefore first review the structural features of the 
Platysomide, genus by genus, and from the facts thus acquired endeavour, in 
conclusion, to justify my views as to their real position, and as to the validity, 
or not, of the suborder established by Professor Younc. 
To those who have kindly aided me by the loan of specimens of this group 
my best thanks are due, especially to Mr Warp of Longton, without the use of 
whose magnificent collection of carboniferous fishes I should not have been 
able to pursue the investigation far. I am also indebted to the Earl of 
ENNISKILLEN, Sir Partie Grey-Ecertron, Professor Huxtey, Professor GEIKIE, 
Professor Hucures, Mr WiriuiAm Davies of the British Museum, Dr RANKIN 
of Carluke, Mr Binney of Manchester, and Mr Puant of Salford for much 
valuable assistance. 
* Bd. i. 2te Halfte, Leipzig, 1875. + Proc. Am. Phil. Soc., May 20, 1877. 
t Carboniferous Ganoid Fishes, part i. Palconiscide, p. 41, “Mem. Paleontographical Society,” 1877. 
VOL. XXIX. PART I. 4uU 
