ges 
Reviews—Dr. Traquair on the Platysomide. 319 
dontid, on account of the form and arrangement of the teeth which 
had been discovered in a mandible of Platysomus macrurus, and also 
upon the conformation and articulation of the scales. This classifi- 
cation was approved by Agassiz, and was favourably received by 
other authors; Geinitz, Pictet, and M‘Coy, in their respective 
systematic works having included the genus in the same family. 
However, Vogt, Heckel, Wagner, and Prof. John Young declined 
to accept this assignment of Platysomus. Vogt still associating 
Platysomus and also Eurynotus with the Paleonisci. Wagner in- 
cludes Platysomus, Dapedius, Tetragonolepis, and his two new genera, 
Homelepis and Heterostrophus, and also Pleurolepis, Quenst., in a new 
family ‘‘ Stylodontes ” which he proposed for their reception ; regard- 
ing which, Dr. Traquair remarks, ‘‘ That the association by Wagner 
of Platysomus with those other genera is just as unnatural as the 
classification which he himself wrote to oppose.” 
Subsequently, Prof. J. Young, who had specially studied Platyso- 
mus and some kindred fishes from the Coal-measures, and upon 
which forms he established the genera Amphicentrum and esolepis, 
“declined to accept the peculiar dentition of Platysomus macrurus as 
characteristic of all the species which had been referred to that 
genus;” he therefore assigns it to a new genus, Hurysomus, and 
makes Platysomus parvulus, Ag. (a Coal-measure species), the type of 
the genus Platysomus ; and states that each of the above genera are 
distinct from, although possessing affinities to, the Pycnodontida. 
He therefore, having reference to the mode of the articulation of the 
scales, proposed a new suborder ‘“ Lepidopleuridx,” containing five 
families, which are mainly founded upon the dentition, and sub- 
divided into two divisions, respectively characterized by the absence 
or presence of the ventral fins. The first division, in which the 
ventral fin is wanting, includes the families PLarysomipa, AMPHICEN- 
TRID#H, and Kurysomrp# ; the second, where the fins are present, con- 
tains MxsoLepipa and Pycnopontipm. These views of Prof. Young, 
as regards the institution of the suborder ‘‘ Lepidopleuride,” were 
also favourably received, among others by Dr. Liitken and Professor 
Victor Carus, but exceptions were taken to some details of arrange- 
ment and classification of the genera composing it. More recently 
Prof. E. D. Cope, apparently unaware of Prof. Young’s investigations, 
places Piatysomus with Dapedius and Tetragonolepis in one family, 
which he terms “ Dapediide,” excluding Eurynotus, which he places 
along with Lepidotus, and Pholidophorus, in the family Lepidotide. 
The preceding summary indicates the interest attached to some 
members of this family of ancient fishes by previous investigators, 
and also the difficulty experienced in providing them with a satisfac- 
tory scientific location and with congenial alliances. Our author 
concludes his introduction by confidently asserting “that the Palzeo- 
zoic 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. Liitken and Prof. Carus in 
uniting them in one family group.” And further, he adds, “ that 
these fishes have little in common with the Pycnodonts, while they 
