DEVONIAN FISHES OF IOWA 169 



1891 . Macropetalichthys sullivanti and M. rapheidolabis E. D. Cope, Proc. U. 

 S. Nat. Mus. 14, pp. 449, 455, pi. 29, 30, fig. 5. 



1897. Macropetalichthys sullivanti and M. rapheidolabis C. R. Eastman, Amer. 

 Nat. 31, pp. 493, 499, pi. 12. 



1901. Macropetalichthys sp. B. Dean, Mem. N. Y. Acad. Sci. 2, p. 119, text- 

 fig. 12. 



1903. Macropetalichthys sp. O. Jaekel, Neues Jahrb. fur Mineral. 1, p. 342. 



1907. Macropetalichthys rapheidolabis C. R. Eastman, Mem. N. Y. State Mus. 

 10, p. 103, pi. 9. fig. 5, pi. 11. 



1907. Macropetalichthys sullivanti E. Hennig, Centralbl. fur Mineral, p. 587, 

 text-fig. 



Headshield suboval, regularly arched in a transverse direc- 

 tion, attaining a maximum length of about 25 cm and width 

 across the posterior border of about 17 cm, but often consid- 

 erably flattened' by pressure. Ornamentation consisting of fine, 

 closely crowded tubercles with stellate bases, sometimes display- 

 ing concentric arrangement. Of the two pairs of small centrals, 

 which are separated from contact with each other by the inter- 

 vention of the median occipital, the anterior takes part in form- 

 ing the orbital border and is not traversed by sensory canals. 

 Pineal plate pierced by an inconspicuous foramen, and appar- 

 ently equivalent to the so-called anterior median element or 

 "mesethmoid" of Neoeeratodus, or to the corresponding undi- 

 vided area in Dipterus. Parasphenoid (or the element inter- 

 preted by Cope as such) much expanded in front, posteriorly 

 produced, resembling in a general way the corresponding mem- 

 brane bone of Ctenodipterines and Sirenoids, but considerably 

 less ossified. Preorbital sensory canals lyrate, and confluent 

 in the middle line with the sharply angulated exoccipito-central 

 system. The postorbital canal extends from the inferior border 

 of the orbits to the center of the marginal plates, where it turns 

 abruptly inward and continues in a straight line to meet the ex- 

 occipito-central canal at the point of its angulation. The latter 

 canal disappears beneath the surface of the external occipital 

 plate on either side close to the hinder margin of the headshield, 

 passing obliquely downward and inward below the cranial roof, 

 and in the living state presumably communicated with the inter- 

 nal auditory sense organs. 



Speaking entirely within bounds, it is not too much to say 

 that the characters of this long misunderstood genus and species 



