380 RAMSAY H. TRAQUAIR ON THE 
somidce, and Mesolepide. These he associated with the Pycnodontide in one 
“ suborder” which he named “ Lepidopleuridz,” and from which he excluded 
Tetragonolepis and Dapedius. 
7. LUTKEN accepted the “ Lepidopleuride,” but divided the series into the 
three groups of Platysomi, Pleurolepide, and Pycnodontide, including in the 
first of these the fishes distributed by Professor Youne in his four families of 
Platysomidz, Amphicentridz, Eurysomidz, and Mesolepide. While admitting 
that the affinity between the Platysomi and Palzonisci is mcontestable, he 
maintained that the former were inseparably allied to the Pycnodonts. 
8. Victor Carus followed LUTKEN in reuniting the Platysomid fishes into 
one family, and in retaining the suborder Lepidopleuride, in which, besides the 
Platysomide, he also included the families of Pycnodontide and Pleurolepide, 
the latter to contain Tetragonolepis, but not Dapedius. 
9. I have myself maintained that the Platysomide are more nearly related 
to the Paleeoniscide than to any other group, and have included both families 
in one suborder with the Chondrosteide, Polyodontide, and Acipenseride. For 
this suborder I have considered the term “ Acipenseroidei” more suitable than 
the Miillerian ‘‘ Chondrostei.” 
10. Professor Core has included Hurynotus along with Palewoniscus, Lepi- 
dotus, Pholidophorus, &c., in the family Lepidotidze, while he has placed Platy- 
somus along with Tetragonolepis and Dapedius in the Dapediide, and retained 
the Pycnodonts as a family by themselves. All these three families are in- 
cluded in his order of Isospondyli. 
The whole question then resolves itself into the following :—In what sort of 
relationship do the Platysomid fishes stand to each of the three families of © 5 
Dapediide, Pycnodontide, and Palzeoniscidee ? 
Relationship to the Dapediide. 
In approaching this question special notice must first be taken of the genus 
Tetragonolepis of Bronn (AGAssiz partim), the peculiar form of whose scales has 
frequently led to its association with the Platysomide, or with the Pycnodontide. 
It is certainly impossible to regard Tetragonolepis as a member of the Pycnodont — 
family, nor can it in any classification be disassociated from Dapedius. On this 
point WAGNER and Cope are undoubtedly right, for the mere fact that the scales 
of Tetragonolepis have their internal rib or keel placed along the anterior 
margin, cannot outweigh the manifest resemblance which it betrays to Dapedius 
in the osteology of the head, in the internal skeleton, and in the form of the 
body and fins. To see that Tetragonolepis has a Dapedioid and not a Pycnodont 
head, one need only look at the beautiful figure of 7. discus given by Sir Pamir 
Grey-Ecerton himself in his paper.on the genus; and as regards the denti- 
