DEVONIAN FISHES OF IOWA 73 



be known in this country by a solitary species occurring in the 

 middle portion of the Salina beds in Perry county, Pennsyl- 

 vania, the horizon being approximately equivalent to the English 

 Ludlow, or to the interval between that and the Wenlock. The 

 great antiquity of this interesting form entitles it to a brief 

 notice in this connection. 



Paheaspis americana Claypole. 



1884. Palceaspis americana E. W. Claypole, Am. Nat. 18, p. 1224. 



1884. Palceaspis bitruncata E. W. Claypole, Ibid., p. 1224. 



1885. Palceaspis americana E. W. Claypole, Quar. Journ. Geol. Soc. 41, p. 62, 



woodcut fig. 7. 

 1885. Palceaspis bitruncata E. W. Claypole, Ibid., p. 62, woodcut fig. 8. 

 1885. Palceaspis bitruncata and elliptica E. W. Claypole, Proc. Amer. Assoc. 



Adv. Sci., 33d Meeting, p. 426. 

 1885. Palceaspis elliptica E. W. Claypole, Rept. Brit. Assoc. Adv. Sci., 54th 



Meeting, p. 733. 



1892. Palceaspis americana E. W. Claypole, Quar. Journ. Geol. Soc. 48, p. 



561, fig. 8. 



1893. Palceaspis americana E. W. Claypole, Amer. Nat. 27, p. 375. 

 1895. Palceaspis americana B. Dean, Fishes, Living and Fossil, p. 71. 



1898. Palceaspis americana A. S. Woodward, Outlines of Vertebrate Pal., p. 6. 



1906. Palceaspis americana M. Leriche, Mem. Soc. Geol. du Nord de la France, 



5, p. 24. 



1907. Palceaspis americana C. E. Eastman, Mem. N. Y. State Museum 10, p. 



29. 



This species, whose synonymy is indicated above, differs from 

 the British P. sericea only in minor particulars, and both ap- 

 proximate very closely to the type of Cyathaspis. In fact, one 

 of the latest students of these forms, M. Leriche, has proposed 

 to unite them in a single genus.* Pteraspis itself, of which the 

 type is P. rostrata (Fig. 7), is strictly European, and common 



Fig. 7. 

 SSFig. 7. Pteraspis rostrata Agassiz. Lower Old Red Sandstone; Great Britain. Left 

 lateral aspect oi partially restored individual, xl. The tail is not certainly known to toe 

 heterocercal. 



to both marine and estuarine, or possibly even fluviatile (Old 

 Eed Sandstone) deposits. 



* Leriche, Maurice, Contribution a P etude des poissons fossiles du Nord de la 

 France et des regions voisines. Mem. Soc. Geol. du Nord de la France, 1906, 5, 

 p. 25.- 



