FAUNE DU CALCAIRE CARBONIFERE DE LA BELGIQUE. 
17 
BENEDENIUS DENEENSIS, P.-J. Van Beneden. 
Palæoniscus de Denée. P. -J. Van Beneden , Bulle lins de l’Académie royale des sciences de Belgique, 
vol. XXXI, 1871, pp. 512-515, pl. IV. 
1 am indebted to my distinguished friend Prof, de Roninck for the opportunity of examining and 
redescribing the unique specimen of this remarkable fish, wbich was figured some years ago by 
M. Van Beneden under the naine of Palæoniscus cle Denée. M. de Roninck having already convinced 
liimself that 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 confîrmed, but also that 
it forms the type of a new genus, whose structural peculiarities demand in addition its entire 
removal from the family 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 % inches, — to the commence¬ 
ment of the lower lobe of the same fin, 8 %; the greatest depth of the body in front of the vendrais, 
or about the middle of the back, is k '/ 4 inches; the depth of the tail pedicle is 1 ‘/ 4 inch. The 
lenght of the head equals its depth at the occiput and is contained 5 '/ â times in the total. 
Head. — The contour of the head descends pretty sharply from the occipital région to the end 
of the snout, which is pointed; the position of the orbit is very clearly indicated, occupying a place 
nearly right over the middle of the lower jaw, and midway between the two extremities of the 
cranium, — it is therefore situated not nearly so far forwards as in the Palæoniscidæ. 
The boundaries of the cranial roof-bones are not easily 
to be made out, nevcrtheless the frontal ff.) and post- 
frontal (p. f.) are évident enough, forming the superior, 
and posterior-superior part of the margin of the orbit, 
whilst between these and the posterior margin of the cra¬ 
nial shield the bony surface exhibited may be referred to 
the pariétal (p.') and the squkmosal ( sq.). A narrow curved 
suborbital (s. of) is very clearly seen, forming the poste- 
rior-inferior margin of the orbit ; but the boues of the nasal 
région hâve been injured and partly split off and removed 
with tbe counlerpart. A strong paraspheroid Çpa. sph.) is 
seen extending along the base of the skull and Crossing 
below the suborbital above referred to. So far as the external surfaces of the cranial roof-bones are 
seen, they are covered with délicate, yet sharply defined, short iuterrupted ridges extending mostly 
in an antero-posterior direction. The position of the hyomandibular suspensorium (Ji. m.) is clearly 
shown, extending downwards and slightly forwards from the squamosal région of the cranium, its 
contour being also slightly curved, with forwardly directed concavity. As regards the bones of the 
gill-cover, that which I interpret as operculum ( op .) is a rather small, nearly square-shaped plate, 
a littîe broader indeed than high, and with rounded postero-inferior angle, placed behind the 
upper extremity of the hyomandibular, and overlapping the middle of the supraclavicxdar (s. cl.). 
Beneath this is a much larger plate (*. 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 3 
