The Catopterus gracilis. 21 



In the arrangement of Agassiz* the Catopterus gracilis would be 

 comprehended in the order of Ganoids and family Lepidoides. 

 Redfield was disposed at first to assign it to the Homocercal divis- 

 ion of Agassiz's family Lepidoides, but was afterwards disposed to 

 qualify this somewhat, and judged it to occupy a sort of inter- 

 mediate position between the two divisions, neither being exactly 

 equilobed, like the Homocerci, nor yet having the decided hetero- 

 cercal character which belongs to those genera which Agassiz has 

 placed in that division. 



The name Catopterus was given to this genus by Redfield, from 

 the situation of the dorsal fin. 



At Little Falls, the bituminous shale in which the fishes are 

 found, occurs interstratified with the sandstone, and is exposed to 

 view at the bottom of a ravine twenty or thirty feet in depth, which 

 has been excavated by the action of a small stream. The stratum is 

 nearly horizontal. Some layers of the shale abound, not only in 

 remains of fishes, but also in those of vegetables, apparently endog- 

 enous, while others are nearly destitute of both. 



The substance of the fish, as well as that of the vegetable, is con- 

 verted into carbonaceous matter, and it is observed that while the 

 form of the scales and rays is perfectly and beautifully preserved, 

 there are no traces of bones remaining. 



According to Agassiz, this is almost universally the case with the 

 individuals of the family Lepidoides to which these belong. 



The following is a description of the Catopterus gracilis: 



Body, fusiform, covered with rhomboidal scales, which extend 

 obliquely across it, and parallel with its length. Scales, middling 

 size. Head, rather small, presenting a finely granulated surface, 

 resembling shagreen. Back, but slightly arched. Pectoral fins, 

 middling. Ventral, small, inserted midway between pectoral and 

 anal. Anal, large. Dorsal, middling, extended opposite the pos- 

 terior part of the anal. Tail, forked, equilobed. Scales, extending 

 a little upon the base of the upper lobe. All of the fins have a se- 



* Agassiz divides fishes into four orders, deriving their characters from the 

 scales: I. The Placoidians, or those whose skin is covered irregularly with 

 plates of enamel. 2. The Ganoidians, or those having angular scales of horny 

 or bony plates, covered with a thick plate of enamel. 3. The Ctenoidians, or 

 those having jagged or pectinated scales. 4. The Cyctoidians, or those having 

 scales smooth and simple at their margin. Three-fourths of the existing species 

 of fish belong to the two last orders, whose existence has not been ascertained 

 below the chalk. The remaining fourth belongs to the two first orders, and ex- 

 isted alone in all the periods during which the fossiliferous rocks below the chalk 

 were deposited. Agassiz: American Journal of Science, Vol. jo ; p. 31). 



