STRUCTURE AND AFFINITIES OF THE PLATYSOMID. 369 
for them the genus Platysomus, which he placed in the “ Lepidoid” family of 
the order Ganoidei. 
For an account of the subsequent history of this genus,—its transference to 
the Pyenodontidee by Sir Puitie Grey-EcErton, to the Stylodontes (Dapediide) 
by Dr AnprEAS WAGNER, and the position assigned to it by Professor Youne in 
his suborder of “Lepidopleuridz,” I may refer to the introduction to this paper. 
Species.—Under Platysomus AGassiz included the species gibbosus and 
rhombus from the German Kupferschiefer ; striatus, parvus, and macrurus from 
the English Magnesian Limestone ; and parvulus and declivus from the British 
coal formation. Professor Kine has merged P. parvus in P. striatus,* and as to 
the so-called P. macrurus (EHurysomus, Young), we have already discussed its 
affinities, and the circumstance that its peculiar dentition, along with the shape 
of the scales, induced Sir Pairie Grey-EGERTON with AGassiz’s approval, to 
transfer not only it, but the whole genus Platysomus to the family of Pynodonts. 
Neither P. parvulus nor declivus were described by Agassiz, but Professor 
Youne has given a minute description of a fish, which, following Professor 
Wit1aMson, he has referred to the former species, and it is chiefly upon its 
structural features that he has based his account of the cranial osteology of the 
genus.t Platysomus declivus isa MS. name given by AGassiz to a specimen 
from Burntisland, Fifeshire, in the collection of Sir Puitip Grey-Ecerron, and 
published by Morris in his “ Catalogue of British Fossils,” p. 339. I am 
indebted to the kindness of its distinguished owner for an opportunity of 
examining the specimen, and find that it is in reality a distorted example of 
Eurynotus crenatus, av opinion in which Sir Pare also concurs. 
By Miunsrert{ three species were added, viz.,—P. Fuldai, intermedius, and 
Althausii, but two of these have been subsequently cancelled. P. Fuldai has 
been merged by GeErnirz§ in P. macrurus (Eurysomus); and there can be no 
doubt that Messrs Hancock and Howsg|| were correct in referring P. Althausti 
to Dorypierus Hoffmanni, Germar. 
From the Coal Measures of Illinois, two species—P. cércularis and P. 
orbicularis—have been determined by Messrs NEwsBerry and WorrTHEN.‘ 
Messrs Hancock and Atruey ** have also added two well-marked Carboni- 
ferous species to the list, viz..—P. Forstera and P. rotundus, from the Coal 
Measures of Newsham, near Newcastle, and I myself must now add still another 
from the Lower Coal Measures of Derbyshire,— 
Platysomus tenuistriatus, sp. nov., Traquair (? = P. striatus, Young pars). 
* Catalogue of the Organic Remains of the Permian Rocks of Northumberland and Durham, 
1848, p. 15 ; “ Permian Fossils” (Mem. Palzontographical Society, 1850), p. 232. 
+ Op. cit. pp. 302-305, woodcut, fig. 2. + Beitriige zur Petrefactenkunde, v. 1842, pp. 43-47. 
§ Dyas, p. 10. || Qu. Journ. Geol. Soc. xxvi. 1870, p. 627. 
J Geol. Survey of Illinois, vol. iv. p. 347, Pl. III. fig. 1 ; Pl. IV. fig. 2. 
** Ann. and Mag. Nat. Hist. (4) ix. 1872, p. 252. 
