DEVONIAN FISHES OF IOWA 175 



mially produced behind.* The extreme thinness of the bone in 

 its anterior portion forms a decided contrast to the solidly ossi- 

 fied plate of Ctenodipterines, and it is further noteworthy that 

 no specimen has yet enlightened us as to its relations with the 

 palato-pterygoid cartilages. Near the point of its greatest con- 

 striction, in what corresponds to the position of the quadrate 

 element in Dipterus, is a well-marked oval concavity, described 

 by Cope as a "glenoid fossa"; and this may not improbably 

 be looked upon as having served for articulation with the man- 

 dibular suspensorium. Nothing whatever is known of the quad- 

 rate, mandibles, or nature of the dentition. These parts must 

 necessarily have existed, and our ignorance of them is attrib- 

 utable to failure of preservation. 



Formation and locality. Onondaga limestone; Le Boy, New 

 York. Columbus and Delaware limestones; Ohio. "Cornifer- 

 ous" limestone of Indiana, and said to have been obtained also 

 from equivalent strata in Canada. Although listed among Ken- 

 tucky Devonian fossils, its reported occurrence within the limits 

 of that State probably rests upon erroneous identification. 



Macropetalichthys agassizi (von Meyer). 



1845. Asterolepis hoeninghausii L. Agassiz (errore). Poiss. Foss. V. G. 



R. p. 130, 147, pi. 30a, fig. 10. 



1846. Placothorax agassizi H. von Meyer, Neues Jahrb. p. 596. 



1847. Placothorax agassizi H. von Meyer, Palseontogr. 1, p. 102, pi. 12, fig. 1. 

 1855. Physichthys hoeninghausii H. von Meyer, Palseontogr. 4, p. 80, pi. 15, 



figs. 1-5 (wow figs. 6-11). 

 1857. Agassichthys agassizi J. S. Newberry, Bull. Nat. Inst. p. 119. 

 1873. Macropetalichthys agassizi J. S. Newberry, Rept. Ohio Geol. Surv., 



Palaeont. 1, pt. 2, p. 291. 

 1895. Macropetalichthys agassizi A. von Koenen, Abhandl. Ges. Wis. Got- 



tingen, 40, p. 22, pi. 4, fig. 3. 

 1907. Macropetalichthys agassizi C. R. Eastman, Mem. N. Y. State Mus. 10, 



p. 112. 

 1907. Macropetalichthys hoeninghausii and Placothorax agassizii E. Hennig, 



Centralbl. fur Mineral. Geol. und Pal. no. 19, p. 587. 



Eeference has already been made to the fact that the type of 

 Hermann von Meyer's Physichthys hoeninghausii is now the 

 property of the Museum of Comparative Zoology at Cambridge, 



*Cope states that "the parasphenoid in both Lepidosiren and Ceratodus is pro- 

 duced abnormally, and it is only necessary to imagine this part to be reduced to 

 its normal length to have the conditions found in Macropetalichthys."— Proc. U. S. 

 Nat. Mus. 1891, 14, p. 455. 



