PALiEONISCIDiE. 
521 
chiostegal bones externally tuberculated or rugose. Pins large, 
consisting of broad flattened rays, all articulated and distally bifur¬ 
cating, more or less coated with ganoine ; anterior borders fringed 
with well-developed fulcra. Dorsal and anal fins triangular in 
shape, elevated, the dorsal opposed to the space between the pelvic 
fins and the anal; caudal fin bifurcated. Scales thick, of moderate 
size, and highly ornamented; not much deeper than broad upon the 
middle of the flank, as deep as broad on the ventral aspect. Each 
scale of the abdominal region marked in the hinder half by coarse 
postero-inferiorly directed ridges and sharp denticulations, in its 
anterior half by few, irregular, more or less interrupted vertical 
ridges and furrows ; the scales of the caudal region coarsely serrated 
posteriorly, with a few short transverse sculpturings anteriorly. 
The form of the upper lobe of the tail in this genus is as yet 
unknown, but the characters of the head appear to justify its refer¬ 
ence to the Palseoniseidse. In the original description of the fish, 
the pelvic fin is referred to as anal, and the anterior margin of the 
latter assigned to the caudal; the supposed absence of an inner 
keel upon the scales of the flank is also now proved to have been 
assumed from imperfect evidence. 
Centrolepis aspera, Egerton. 
1844. Centrolepis asper, L. Agassiz, Poiss. Foss. vol. ii. pt. i. p. 304 
(name only). 
1858. Centrolepis asper , Sir P. Egerton, Figs. & Descrips. Brit. Organic 
Remains (Mem. Geol. Surv.), dec. ix. no. 5, pi. v. 
1890. Centrolepis asper, A. S. Woodward, Ann. Mag. Nat. Hist. [6] 
vol. v. p. 430, pi. xvi. fig. 1. 
Type. Portion of head and trunk, with paired fins; British 
Museum. 
The type species, attaining a length of about 0*25-0*3, Maxi¬ 
mum depth of trunk equal to length of head with opercular appa¬ 
ratus, and contained nearly four times in the total length; snout 
prominent and bluntly pointed; teeth long, slender, and acute, 
sometimes gently curved; cranial roof ornamented with closely 
arranged rounded tubercles, the posterior expansion of the maxiila 
with similar tubercles and rugae, and the mandible with irregular 
delicate striations, mostly directed longitudinally and sometimes 
passing into small tubercles ; operculum, suboperculum, branchio- 
stegal rays, and exposed portions of the pectoral arch also tuber¬ 
culated, the clavicle sometimes in part rugose. Pelvic fins not 
much inferior in size to the pectorals, arising behind the middle 
