606 BRITISH PALAXOZOIC FOSSILS. [ Pisces. 
exceeding the depth of the body by one-third ; orbits large ; lateral line strongly marked slightly nearer to the 
dorsal than to the ventral margin; scales oblong, a little deeper than long, nearly equal all over the body, 
except on the upper lobe of the tail, where they become acutely rhombic, and about twice as long as deep ; 
all about the middle of the body a space of two lines would include four scales in depth and five in length; a 
space equal to the depth of four scales is exceeded four and half times by the depth of the body at same 
place (Agassiz’ figure having the scales too large, but Prof. King’s being correct); surface of the scales 
when strongly magnified shewing a few faint longitudinal strize and minute punctures ; posterior edge crenated 
except towards the end of tail, where they become smooth ; the upper and lower margins almost straight, very 
slightly sigmoid; fins small, space between origin of pectorals and origin of ventrals slightly less than from 
origin of ventrals to origin of caudal; from the origin of ventrals to origin of anal fin, equal to the depth of the 
body at ventrals; caudal deeply forked ; lobes narrow, elliptical, equal, length of the lower lobe equalling the 
depth of body at the nape or at the ventral fins; average length five inches two lines, greatest depth of body 
eleven lines, diameter of orbit two and half lines. 
The above description is from the original specimen, but the state of the surface is such that I cannot 
distinguish the radiating furrows said to mark all the bones of the head. 
Position and Locality.—Very rare in the Permian marl-slate of East Thickley. 
PaL#oniscus FREIESLEBENI (De Blain.) 
Ref. and Syn.= Paleothrissum macrocephalum + P. magnum de Blain. and Sedgwick, Trans. Geol. Soc. 2nd Series, 
Vol. III. t. 8. f. 1, 2. t. 9. f. 2.= Paleothrissum Freieslebense de Blain. Dic. d’Hist. Nat. Vol. XXVIII. 
= Paleoniscus megacephalus Germ. =P. Freieslebent. Ag. P, F. Vol. II. t. 11, 12. + P. comptus Ag. id. 
t. 103. f.1, 3; King, Perm. Foss. t. 21. f. 1. 
Dese.—V ery elongate, ovate, or lanceolate; head large, nearly one-fourth the entire length (the upper lobe 
of tail extending one-third the length of the head beyond four lengths of the head from the snout); length of 
head exceeding the depth of the body at nape by about one-fifth; lower jaw short ; pectorals small; the space 
from origin of pectorals to origin of ventrals exceeds the greatest depth of the body between these fins by one- 
tenth; from origin of ventrals to anal fin exactly equalling the depth of body at origin of the former; from 
origin of anal to origin of caudal fin slightly less than from origin of ventral to origin of anal, but exactly 
equalling the depth of the body opposite the latter point; dorsal fin small, situated a little behind the ventrals, 
triangular, slightly rounded; depth of pedicle of tail at origin of caudal equal to half the depth of body to 
origin of ventral fins; tail deeply forked; upper lobe narrower and considerably longer than the lower. Scales, 
oblong, very uniform over nearly the whole body, about one-third deeper than long on the flanks in front of the 
ventrals, where a space equalling four scales in depth, or seven in length, is about equal to one-fourth the 
depth of the body (within the size of one scale) ; behind the ventrals their length remains exactly the same, 
nearly to the origin of the caudal, but the depth is reduced to an equality therewith; on the upper lobe of the 
tail the scales as usual assume a very elongate acutely rhombic form ; all the scales marked with fine, irregular, 
slightly flexuous ridges, and finely fringed on the posterior margin; the upper and lower edges of the scales 
nearly straight, or with a very faint sigmoid curvature. Length of average specimen eight inches five lines; 
depth of body one inch six lines ; in middle of flanks in front of ventrals three scales in depth, or six in length, 
occupy a space of four lines over anal fin; the same space includes the same number in length, but rather 
more than five in depth. 
The entire of the above description was drawn from one of Prof. Sedgwick’s typical specimens from East 
Thickley, and every portion of it compared at the same time, both in measurements, proportions and sculpturing 
of the body, fins, and scales, with a specimen of the same size of the Paleoniscus Freieslebeni from the Richels- 
dorf copper-slate, and they agree to the most minute particular; I have therefore no hesitation in asserting 
confidently the perfect identity of the English marl-slate species, and that of the German copper-slate, 
contrary to the writings of M. Agassiz, but fully bearing out the statement to this effect by Prof. Sedgwick 
and M. de Blainville, in the above quoted Memoir of the former on the Magnesian limestone of England. 
