748 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. [2] 



PART I. 



Ever since 1845 — when Garl Yogt^ demonstrated that Amia calva, L 

 diftered in the structure of its heart from all known bony fishes, being 

 like the cartilaginous fishes in this respect; and since Johannes Mliller,* 

 noting this circumstance, separated this remarkable fish from the 

 Clupeoids,«with which it had formerly been classed, adding it to his and 

 L. Agassiz's established sub-class of Ganoids — the attention of anat- 

 omists has been steadily directed towards this form. 



A number of works touching upon nearly all parts of the anatomy of 

 Amia have made their appearance, so its structure is at present better 

 known than that of most bony fishes. It is quite remarkable that the i 

 cranial anatomy of this Ganoid has not received, proper attention, as it 

 is by no means a rare fish in collections. The memoir hj Bridge,* pub- 

 lished in 1877, is in my opinion the only one in which the subject has 

 been at all fully described. 



Upon the suggestion of Privy Counselor Professor Gegenbaur, I 

 undertook the task of re-examining the crania of the Teleostei, especially 

 in the Physostomi and the Anacanthini, and in looking for a form in 

 which the various differences in the structure of the skull could best be 

 judged, my attention was drawn to Amia. In fact, a careful study of 

 the cranium of this fish showed that several diverging series of skull- 

 types could easily be traced from it. On the other hand, the task of 

 tracing the conditions of the cranium of the Teleostei from more simply 

 constructed types — such as the Selachians offer — I found the Amia to be 

 an excellent transitory form for the purpose. The careful descriptive 

 work of Bridge, with whom I concur in the majority of points, so far 

 as the actual conditions are concerned, does not suffice for this special 

 purpose. Certain points of organization, which at the first glance ap- 

 pear to be incorrect, and the significance of which only become appar- 

 ent after comparisons with other forms, he has left entirely unnoticed. 

 Furthermore, in his descriptions he has kept strictly within the limits 

 of his title, perhaps for lack of material, describing only the bones of 

 the skull and entirely neglecting the surrounding soft parts, in which 

 I recognize the necessary elements to complete the configuration of the 

 skull. Finally, in my opinion. Bridge has not been fortunate in his 

 descriptions of several of the bones of the skull in Amia. 



Taking all this into consideration, I decided to present a comparative 

 description of the skull of Amia. At the same time I believe I will be 



^Annales des Sciences Naturelles, T. IV, 1845. (I have changed the numbering of Dr. 

 Sagemehl's foot-notes so as to accommodate them to the present article. — Trans.) 



" Vber den Ban nnd die Grenzen der Ganoiden. Ahh. d. k. Akad. d. Wissenachaften z. 

 Berlin vom Jahre 1844. Berlin, 1846. Nachschrift, pag. 204. 



^The Cranial Osteolc^y of Amia calva. Jonrn. of Anatomy and Physiology, Vol. 

 XI, 1877, pages 605-622. 



