oo Bulletin American Museum of Natural History. [Vol. XIX, 



have not been removed from their natural position. If so 

 the base of the fin is placed between the 5th and 6th verte- 

 brae in front of the first caudal. The fin itself is overlaid 

 with fragments of ribs, so that the number of 

 its rays cannot be accurately determined, but 

 there were at least eight of them, the most 

 anterior one being apparently rudimentary. 



At the upper ends of the 4th and 5th caudal 

 vertebrae are two bones which resemble inter- 

 neurals with enlarged upper ends. They may 

 represent the supports of the dorsal fin. They 

 Fig. 72. Em^o ne- ^^6 rathcr weak and may be the more pos- 

 pakoiica cop^. N^o. ^^^-^j. ^^^^ ^^ ^-^^ sexie^. In the region of the 



^vent^affins".'''""^'^ thrcc Or four most anterior haemal arches are 

 slender bones which may have been the sup- 

 ports of the anal fin. 



No. 2032 of the American Museum of Natural History 

 furnishes most of the tail fin (PL I, Fig. 4). The principal 

 rays are large and coarsely segmented, but distally the rays 

 divide into extremely fine filaments. The lobes of this fin 

 were probably about 175 mm. in length. 



The following fishes, as well as Spaniodon simus, described 

 on page 47 were, as we learn from Prof. Cope (Bull. U. S. 

 Geol. and Geog. Surv. Terrs., IV, 1878, p. 66), collected by 

 Dr. F. V. Hayden in the "Niobrara Cretaceous of Dakota." 

 No more accurate information has been afforded us regarding 

 the locality where these specimens were found ; but on several 

 of the blocks of soft limestone, on which these fishes are pre- 

 served, some person has written in lead pencil the words 

 "Yankton, Neb." From this label we may be quite sure that 

 the specimens were found in the region of Yankton, South 

 Dakota. We know likewise that the Niobrara deposits are 

 abundantly developed in that region. 



These fishes are of great interest from the fact that they 

 belong to genera found in Upper Cretaceous deposits at Mount 

 Lebanon, in Syria, or to genera very closely related to those 

 of the latter region. It is greatly to be desired that further 

 search shall be made in the country about Yankton for more 



