PLATTS0MATIDJ5. 527 
now re-named Styracopterus fulcratus , without definition (R. H. 
Traquair, Ann. Mag. ]S T at. Hist. [6] vol. vi. 1890, p. 492). 
Generically indeterminable remains, probably of Palseoniscidse, 
are also named thus:— 
Turseoclus acutus , J. Leidy, Proc. Acad. Nat. Sci. Philad. 1857, 
p. 167.—Triassie(?); Phoenixville, Chester Co., Pa. [Jaw;^, ^ ^ 
Academy of Sciences, Philadelphia.] ? % 
/96'7- 
resets# ■ 
Urosthenes australis, J. D. Dana, AmefT Journ. Sci7[2j vol. v?\ — 
(1848), p. 433.—Hawkesbury Series; New South Wales. 
[Tail; accidentally destroyed by fire.] 
Isocfus leptognathus, P. M‘Coy, Ann. Mag. Nat. Hist. [2] 
vol. ii. (1848), p. 3.—Lower Carboniferous; Moyheeland, 
Draperstown, Ireland. [Dentary bone ; Dublin Museum,J 
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Family PLATYSOMATIDiE. 
Trunk deeply fusiform or irregularly rhombic ; tail heterocercal; 
scales rhombic, ganoid, firmly united with peg-and-socket articula¬ 
tions. Head-bones well developed, ganoid ; no median series of 
cranial roof-bones; eye far forwards and high in position; snout 
prominent; mandibular suspensorium nearly vertical, slightlv 
inclined downwards and forwards in the more specialized genera. 
A series of broad branchiostegal rays, with a small anterior 
azygous element at the symphysis of the mandible. Dorsal fin 
single, much extended. 
As remarked in an elaborate memoir by Traquair 1 , the osteology 
of the genera of this family, so far as known, is identical with that- 
of the genera of Palseoniscidse, the only essential difference being 
that in the present case specialization results in the extreme 
deepening of the head and trunk, whereas in the last-mentioned 
family the result is remarkable elongation of the whole body and 
the widening of the gape of the mouth. The typical Platysomatidte 
have short, stout jaws, with a chiefly tritoral dentition; while the 
Paheoniscidse are chiefly rapacious fishes, with conical laniaries. 
It is also worthy of note that in the only typical genus in which 
the endoskeleton of the trunk has been clearly observed ( Platy - 
somus ), the double series of robust dorsal fin-supports extends far 
in advance of the origin of the fin itself. The same arrangement is 
distinctly exhibited in the problematical Permian fish, Dorypterus , 
1 R. H. Traquair, “ On the Structure and Affinities of the Platysomidre,” 
Trans. Roy. Soc. Edinb. vol. xxix. (1879), pp. 343-391, pis. iii.-vi. 
