368 RAMSAY H. TRAQUAIR ON THE 
The orbit (or.) is placed right over the middle of the mouth; a conspicuous 
sickle-shaped suborbital bounds it below and behind, while another (the so- 
called lachrymal), larger and broader, completes it below and in front ; besides 
which there is evidence of a narrow superorbital chain placed along the outer 
orbital margins of the posterior and anterior frontals, which I rather suspect is 
continued as a circumorbital ring round its entire circumference. The opercular 
bones and branchiostegal rays are extremely similar in form and relations to 
those of Hurynotus. So likewise are the bones of the shoulder-girdle, which 
include well-marked in/fraclaviculars, but the post-temporal seems to be rather 
small. 
Occasional traces of a pretty well ossified internal skeleton may occasionally be 
seen shining through the dense scaly investment in small specimens. They are 
too imperfect to admit of detailed description; but so far as they go they seem to 
indicate that the conditions were pretty similar to what exists in Platysomus. 
Remarks.—The remarkable genus just described betrays a most singular 
resemblance to Hurynotus in the shape of the cranial bones, while in the form 
of the body it is more akin to Platysomus; and in that of the scales we find the 
“ Lepidopleurid ” type carried to an extreme. The dentition is, however, alto- 
gether peculiar, and forms a forcible illustration of the small systematic value 
of the external configuration of these organs; and I also fail to see how, accord- 
ing to Professor Youne, ‘‘ Amphacentrum gives the explanation of the arrange- 
ment” found in Pycnodus.* 
Genus VII. Platysomus, Agassiz, 1835. 
Stromaieus, Blainville, Germar. 
Uropteryx, Agassiz. 
History.—The deep-bodied fishes of the Kupferschiefer were well known to — 
the older German writers in the beginning of last century, such as Knorr and 
WALCHNER, ScHEUCHZER, Myttius, and Wotrart. Paleontology was, however, 
then in its infancy, and these pioneers of modern science, misled by the broad 
rhombic shape of these fishes, were content to consider them as petrified turbots, 
“Rhombus,” or in German, “ Meerbiitt,” “ Platteiss,” “ Scholle”). Specially 
worthy of note is the excellent figure given by WotFrart (“ Historia Naturalis — 
Hassize inferioris,” pt. i. tab. xiii.) of a “ Rhombus major diluvianus” (Platysomus 
rhombus, Agassiz), in which the general form of the body, of the scales, and of — 
the deeply-cleft heterocercal tail, the latter part being certainly very unlike the’ 
caudal fin of a Rhombus, are well brought out. Afterwards they were referred 
by De Bianvite and by Germar to the genus Stromateus, but it was reserved 
for AcAssiz to point out their dissimilarity to all existing forms, and to institute 
* Op. cit. p. 312. lf 
