fin of the two, and is placed entirely in advance of the anal. In the dorsal 
fin, the most anterior rays gradually increase in length to the twelfth, which 
is longest, and the rapid shortening of those that follow is snch as to make 
the posterior margin mnch more abrupt than the anterior; in the anal tin, 
the maximum length is attained by about the ninth ray, and the shortening 
of the rays in either direction is precisely like that observed in the dorsal. 
Each of these fins is distinctly sup])orted by a series of stout interspinous 
bones, Avith somewhat expanded extremities, much less numerous than the 
rays ; the anal fin of the type-specimen exhibiting only ten bones a])posed 
to at least twenty-five of the rays. 
The caudal fin (PI. TV, Pigs. 1, 3) is deeply forked, and the loAver lobe 
consists of about forty rays. 
All the fin-rays arc delicate, laterally compressed, and articulated at 
more or less distant intervals ; and many, if not all, are bifurcated distally. 
In the best preserved fins there are no indications even of minute fulcra. 
Squamatlon. — The scales of the flanks arc extremely delicate, rhom- 
l)oidal in form, as deep as broad, and ornamented by two prominent diagonal 
ridges, Avhich are not parallel, but often meet in front and arc most Avidcly 
separated mesially. In most specimens the obscure remains of these ridges 
constitute the only evidence of the original presence of scales ; bnt one small 
fossil. No. e, is more satisfactory, and a fcAV of the actual scales arc shoAvn, of 
six times the natural size, in PI. IV, I'ig. 4. The scales upon the sides of the 
upper caudal lobe (PI. IV, Pigs. 1, 3) arc much thicker than those of the 
remainder of the body. They also exhibit the characteristic oat-shaped form, 
and arc diagonally ridged. 
(ii)— Caudal fin senii-heterocercal. 
Family — CATOPTERIDiE. 
Fam. Char. — Body elongate ; scales rhombic, enamelled ; dorsal fin 
remote ; head-bones Avell developed, externally enamelled ; eye far fonvards, 
and snout prominent ; suspensorium oblique, and mouth deeply cleft. 
Ohs . — The genera Catopterus, Pvedfield,* and Fictyopyge, Egertoipf 
liaA'C been associated in recent years with Acentrophorns and Semionotus 
* J. H. Redfield, “ On the Fossil Fishes of Connecticut and Massachusetts,” Ann. Lyc. Nat. Hist. New 
York, 1848, A^ol. iv, p. 37, I’l. i. 
+ In C. Lyell, “ On the Structure and Probable Age of th(? Coal-fleld of the .Tames River, near Richmond, 
Virginia,” Quart. Journ. Geol. Soc., 1817, Vol, hi, p. 27(>. 
