THE STRUCTURE OF DIHICHTHTS 

 A CONTRIBUTION TO OUR KNOWLEDGE OF THE ARTHRODIRA 



By Anatol Heintz 



Curator of the Paleontological Museum, 



Oslo, Norway 



INTRODUCTION 



As we know, Newberry, in 1868, described the first fragments of Dmichthys (D. 

 herzeri). Since that time, nearly ninety larger and smaller papers on Dmichthys have 

 been published by various American scientists. Of these Newberry published 15; Adams, 

 1; Branson, 4; Bryant, 1; J. M. Clarke, 3; W. Clark, 1; Claypole, 11; Dean, 12; East- 

 man, 18; Hussakof, 10; Moodie, 1; Ringeberg, 1; Smith, 2; Stetson, 1, and Wright, 2. 

 Among these publications, nearly all of Newberry's and Dean's, and many of Hussakof 's, 

 are descriptions of and observations on the material preserved in the American Museum 

 of Natural History. 



I also have had the privilege of studying these remarkable collections and have been 

 successful in finding some new points in the structure of Dmichthys, and have been able to 

 make a new reconstruction of this form. Doctor William King Gregory, Professor of 

 Vertebrate Palaeontology in Columbia University and Curator of Ichthyology in the 

 American Museum of Natural History has been good enough to propose to me this 

 publication of the results of my investigations. 



In this place 1 wish to express my deep gratitude to my teacher and friend. Professor 

 Johan Kiaer, of the University of Oslo, for all the kindness he has shown me, and for his 

 constant help. Only through his efforts was I able to come to America. 



I also desire to express my best thanks to Professor Gregory for the privilege of study- 

 ing in the American Museum and for all the benevolent interest he has shown my work, 

 and I am also obliged to Dr. L. Hussakof, Research Associate in Devonian Fishes in the 

 Museum, for his friendliness during my studies in America. I am especially grateful to 

 Miss Francesca La Monte, Assistant Curator, for the constant help and unusual kind- 

 ness she has shown me. 



During the summer of 1930, I visited the Cleveland Museum of Natural History, 

 the Museum of the Buffalo Society of Natural Sciences, and the Museum of Comparative 

 Zoology at Harvard University. In all these institutions I was permitted to study the 

 collections of Arthrodira, and I here wish to express my gratitude to the authorities of 

 these museums for their courtesies. 



The material in Cleveland, Ohio, gathered under the direction of Professor J. E. 

 Hyde, is the most perfect collection of Arthrodira I know. However, since it is going to 

 be described in a monograph by Professor Hyde, nothing I saw in Cleveland is included 

 in this work. I might only mention here, however, that in spite of Professor Hyde's far 

 superior material, and in spite of some new plates of Dinichthys he has found, the descrip- 

 tions given in this paper correlate perfectly with the new material in Cleveland. I am 



