348 L. Ilussakof—Note on a Palteoniscid Fish. 



Cope described seven species, representing rive genera, from a 

 Cretaceous horizon, collected by the Hayden Survey of the 

 Territories. They included two new genera, Tricenaspis and 

 Ichthyotringa ; and the species, as a whole, showed a marked 

 resemblance to the Cretaceous fauna of Mount Lebanon. In 

 1891,* Cope described five species from the Black Hills region, 

 three of them representing new genera. One form was a new 

 species of Mioplosus, a genus previously known only from the 



Fig. 1. 

















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nS®Hk ' * **■ ■ 



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■ v i3nK 









■Pfb^ ""-',1 



HliiP^ 







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'**--<-7j^L^j 



s 



A palasoniscid fish from the Minnekahta limestone (Permian), near Rapid 

 City, S. D. x 3/5. 



Green River shales of Wyoming. This fact, and also the 

 absence of Cretaceous forms, led Cope to believe that the speci- 

 mens were from a Tertiary horizon ; and the resemblance of 

 the matrix to that of the White River formation, led to the 

 conclusion that the horizon was probably Oligocene. JN~o 

 further light has ever been thrown on these species, and. no 

 additional specimens have, to my knowledge, been obtained. 



A third record of South Dakota fishes was given in a short 

 paper by C. R. Eastman, in 1899. f He figured several speci- 

 mens from a Jurassic formation in the Black Hills region, 

 among which he recognized two species, named by him Pho- 

 lidophorus americanus and Amiopsis f dartoni. No other 

 examples of these species have since been obtained. 



The fishes from the Minnekahta limestone diifer from all pre- 

 viously described and are of an earlier age, namely, Permian. 



Description of specimens. — The better of the two specimens 

 is a fish lacking the caudal extremity, and without any of the 



* Cope, E. D., On some fishes from South Dakota, Amer. Naturalist, xxv, 

 654-658, 1891. 



f Eastmau, C. R., Jurassic fishes from [the] Black Hills of South Dakota, 

 Bull. Geol. Soc. Amer., x, 397-408, pis. 45-48, 1899. 



