240 IOWA GEOLOGICAL SURVEY 



Finally, concerning the extraordinary conservatism and per- 

 sistency manifested by the family ever since its introduction, 

 the illustrious English biologist whom we have already quoted 

 expresses himself in following terms :* 



"Bearing in mind the range of the Coelacanths from the Car- 

 boniferous [since ascertained to extend from the Devonian] 

 to the Chalk formations inclusive, the uniformity of organiza- 

 tion of the group appears to be something wonderful. I have 

 no evidence as to the structure of the base and side walls of the 

 skull in Coelacanthus, but the data collected together in the 

 present Decade shows that, in every other particular save the 

 ornamentation of the fin-rays and scales, the organization of the 

 Coelacanths has remained stationary from their first recorded 

 appearance to their exit. They are remarkable examples of what 

 I have elsewhere termed ' ' persistent types ' ', and, like the Laby- 

 rinthodonts, assist in bridging over the gap between the Palae- 

 ozoic and the Mesozoic faunae." 



Genus COELACANTHUS Agassiz. 



Supplementary caudal fin prominent; the rays of all the fins 

 long and slender, without denticles or tuberculations, unjointed 

 for a considerable length proximally, but closely articulated dis- 

 tally without being expanded. Superficial ornament of external 

 bones and scales consisting of more or less discontinuous fine 

 ridges of ganoine, sometimes broken up into a series of tubercles. 



The earliest known representative of this genus is a small 

 form occurring in the lower part of the Upper Devonian near 

 Gerolstein, in the Eifel District, first described by von Koenenf 

 in 1895, and referred by him with some hesitation to Holopty- 

 chius, but afterwards recognized by Smith Woodward^ as a 

 typical Coelacanth. On the basis of that interpretation the 

 form is to be recorded as C. kayseri (von Koenen). Prior to its 

 discovery the opinion had been generally entertained that, owing 

 to the sudden appearance of Coelacanth fishes in a complete 

 state of development in the Calciferous sandstones of Scotland, 



* Memoirs of the Geological Survey of the United Kingdom, Decade XII. 1866. 

 Reprinted in the supplementary volume of the "Scientific Memoirs of Thomas 

 Henry Huxley" (1903), p. 65. 



tVon Koenen, A., Ueber einige Fischreste des norddeutschen und bohmischen 

 Devons. Abhandl. k. Ges. Wiss. Gottingen, phys. CI. (1895), 40, p. 28. 



t Woodward, A. S., Note on a Devonian Coelacanth Fish. Geol. Mag. (1898), 

 Dec. 4, vol. 3, p. 529. 



