DEVONIAN FISHES OF IOWA 243 



nized genera, among which the most satisfactorily known are 

 Coelacanthus proper, Macropoma and Undina. The typical 

 genus enjoys the truly remarkable range from the Upper De- 

 vonian to the close of the Palaeozoic, and if the evidence of one 

 or two doubtful forms be accepted, possibly even higher; the 

 remaining genera extend throughout the Mesozoic, and exhibit 

 such constancy of structural characters that the family has been 

 frequently cited as one of the most distinct and well defined in 

 the animal kingdom. Huxley, for instance, drew attention to its 

 singular compactness in the following paragraph:* 



"The Coelacanthini, as thus understood, are no less distinctly 

 separated from other fishes than they are closely united to one 

 another. In the form and arrangement of their fins; the struc- 

 ture of the tail and that of the cranium; the form and number 

 of the jugular plates; the dentition; the dorsal interspinous 

 bones; the pelvic bones; the ossified air-bladder; the Coelacan- 

 thini differ widely from either the Saurodipterini, the Grypto- 

 dipterini, or the Ctenodipterini ; but, on the other hand, they 

 agree with these families and differ from almost all other fishes, 

 in the same respects as those in which the several families just 

 mentioned have been shown to agree with one another ; viz., the 

 number of the dorsal fins, the location of the paired fins, the 

 absence of branchiostegal rays and their replacement by jugular 

 bones." 



It will be instructive in this connection to compare the views 

 of the elder Agassiz in regard to the family as originally de- 

 fined by him, and also regarding Coelacanthus itself, the fol- 

 lowing passage being taken from Huxley's translation of a por- 

 tion of pages 168 and 170 of the second part of the second volume 

 of the "Recherches sur les Poissons Fossiles" : 



Agassiz on the "Family of the Coelacanths ". 



"I unite in this family many genera of an altogether peculiar 

 physiognomy, but with whose true affinities I am, as yet, only 

 very imperfectly acquainted. A remarkable peculiarity which 

 has struck me in most of these fishes is the circumstance that 

 their bones, and notably their fin rays, are all hollow internally, 

 a peculiarity which is not met with in other ganoids, and which 



* Huxley, T. H., Preliminary essay upon the systematic arrangement of the 

 fishes of the Devonian Epoch, prefixed to the tenth decade of the "Figures and 

 Descriptions illustrating British Organic Remains" (1861), p. 20. 



