IOWA GEOLOGICAL SURVEY 



We are justified in expressing surprise at these features, for 

 not only is their occurrence singular for the family of Coela- 

 canths in general, but they have not hitherto been known to be 

 combined in any Palaeozoic fish. Eel-shaped forms occur in a 

 few groups, mostly sharks, during the Palaeozoic, as has already 

 been noted in treating of Cladoselache and Acanthodians ; and it 

 will be remembered that this form of body has been interpreted 

 as a symptom of decadence.* These forms do not, however, 

 develop continuous median fins. Contrariwise, Phaneropleuron 

 and Uronemus furnish examples among Palaeozoic Dipnoans 

 where the unpaired fins are confluent, but the form of body is 

 massive and cylindrical, and hence can hardly be described as 

 eel-shaped. Typical eels, as every one knows, do not occur until 

 the Upper Cretaceous. 



In so far as the specimen before us is remarkable for exhibit- 

 ing the combination of characters just described, precisely on 

 that account is it difficult to affiliate it with other contemporary 

 forms of fish life with which we are familiar. Its reference to 

 Coelacanths is admittedly provisional. Yet at the same time we 

 cannot deny that its affinities are more readily to be sought 

 in the vicinity of this group than any other. Grounds for this 

 belief are to be found in the delicately striated scales of the new 

 form, the posterior prolongation of the body axis, and its ossified 

 neural and haemal spines, features which offer suggestive points 

 of comparison with typical Coelacanths. One will recall also, 

 that at least one undoubted member of the family, C. exiguus,-\ is 

 of about the same size, has degenerate squamation, and accom- 

 panies the present form in the same fauna. On the whole, the 

 most plausible interpretation of Palaeophichthys seems to be to 

 regard it as an aberrant and extremely degenerate offshoot of 

 fringe-finned ganoids adapted to a mud-grovelling mode of 

 existence. 



Formation and locality. Coal Measures ; Mazon creek, Grundy 

 county, Illinois. 



*Cf. ante, p. 61. 



t Described in Journal of Geology (1902), vol. 10, p. 538, text-fig. :). 



