FAUNE DU CALCAIRE CARBONIFERE DE LA BELGIQUE. 
17 
BENEDENIUS I1ENEENSIS, P .- J . Van Beneden. 
Palæoniscus de L)e née. P. -J. Van Beneden, Bulletins de l’Académie royale des sciences de Belgique, 
vol. XXXI, 1871, pp. 512-515, pl. IV. 
I am indebted to my distinguished friend Prof, de Koninck for the opportunity of examining and 
redescribing the unique specimen of this remarkable fish, wbich was figured sonie years ago bv 
M. Van Beneden under the naine of Palæoniscus de Denée. M. de Koninck having already convinced 
bimself tbat it was not a true Palæoniscus, kindly forwarded the specimen to me, and on exami¬ 
ning it, 1 fînd this opinion concerning its generic position not only fully confirmed, but also lhat 
it forms the type of a new genus, whose structural peculiarities demand in addition its entire 
removal frorn the familv of Palæoniscidæ. 
«/ 
General proportions. — The body is pretty deep, ovoid in shape, the dorsal and ventral con¬ 
tours being pretty evenly arched as far as the tail pedicle. The entire length of the specimen from 
the tip of the snout to that of the upper lobe of the caudal fin is 11 s / 4 inches, — to the commence¬ 
ment of the lower lobe of the same fin, 8 '/ â ; the greatest deplh of the body in front of the ventrals, 
or about the middle of the back, is k> */ 4 inches; the deplh of the tail pedicle is 1 ’/ 4 inch. The 
lenght of the head equals its deplh at the occiput and is contained 5 fi mes 1(1 fh e tota *- 
Ilead. — The contour of the head descends pretty sharply from the occipital région to lhe end 
of lhe snout, which is pointed; the position of the orbit is very clearly indicated, occupying a place 
nearly riglit over the middle of the lower jaw, and midway hetween lhe two extremities of the 
cranium, — it is therefore situaled not nearly so far forwards as in the Palæoniscidæ. 
The boundaries of the cranial roof-hones are not easily 
to he made out, nevertheless the frontal (/”.) and post- 
frontal [p. /'.) are évident enough, forming the superior, 
and posterior-superior part of the margin of the orbit, 
whilst hetween these and tlie posterior margin of the cra¬ 
nial sliield the hony surface exhihited may he referred to 
lhe pariétal [p.) and the squainosal (sq.). A narrow curved 
suborbital (s. o .) is very clearly seen, forming the poste- 
rior-inferior margin of lhe orbit; but the boues of the nasal 
région hâve heen injured and partly split off and removed 
with the counlerpart. A strong paraspheroid fpa. sph .) is 
seen extending along the hase of the skull and Crossing 
below the suborbital above referred to. So far as the external surfaces ofthe cranial roof-hones are 
seen, lhey are covered with délicate, yet sharply defined, short interrupted ridges extending mostly 
in an antero-poslerior direction. The position of the hyomandibular suspensorium (Ji. ni.) is clearly 
shown, extending downwards and slightly forwards from the squainosal région of lhe cranium, its 
contour being also slightly curved, with forwardly directed concavity. As regards the bones of the 
gill-cover, that which I interpret as operculurn (op .) is a rather small, nearly square-sliaped plate, 
a little hroader indeed than higli, and with rounded postero-inferior angle, placed behind the 
upper extremity of the hyomandibular, and overlapping the middle of the supraclavicular [s. ci). 
Beneath this is a much larger plate fi. op.) forming the greater part of the gill-cover, and which 
seems to correspond with the plate which, in the Palæoniscidæ was formerly considered as 
IL 
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