226 IOWA GEOLOGICAL SURVEY 



Formation and locality. Cat skill sandstone (Chautauquan; ; 

 Tioga county, Pennsylvania, and Delaware county, New York. 



Dipterus sherwoodi Newberry. 



1875. Dipterus sherwoodi J. S. Newberry. Kept. Ohio Geol. Surv., Palseont. 



2, pt. 2, p. 61, pi. 58, fig. 17. 

 1889. Dipterus (Ctenodus) sherwoodi J. S. Newberry. Monogr. U. S. Geol. 



Surv. 16, p. 118, pi. 27, fig. 32. 



1907. Dipterus sherwoodi C. R. Eastman, Mem. N. Y. State Museum, 10, 



p. 162. 



1908. Dipterus sherwoodi L. Hussakof, Bull. Amer. Mus. Nat. Hist. 25, p. 52. 



Of this species no other examples are known but the type speci- 

 men, which is imperfect. In the text of Newberry's monograph, 

 this is determined as "apparently one of the upper palate teeth 

 of a species of Dipterus," but in the explanation of figures it 

 is identified as a mandibular dental plate. It agrees with the pre- 

 ceding species in having a coarse tuberculation and very few 

 ridges, some of them indistinct. The tubercles themselves are 

 stated to be "somewhat compressed laterally, rounded, smooth, 

 and blunt at the summit. ' ' 



Formation and locality. Catskill sandstone (Chautauquan) ; 

 Tioga county, Pennsylvania. 



Dipterus murchisoni Pander. 

 (Plate II, Fig. 10) 



1858. Dipterus murchisoni C. H. Pander, Ctenodipt. devon. Systems, p. 23, 



pi. 7, fig8. 2-4. 

 1900. Dipterus murchisoni C. R. Eastman, Centralbl. fur Mineral. 1900, p. 



177. 



It is of interest to note the present species in this connection 

 on account of its geographical distribution and undoubted ma- 

 rine habitat, in which latter respect it agrees with State Quarry 

 Dipterines, and differs from American Chemung and Scottish 

 Old Red Sandstone species. Apparently indigenous in the 

 Russian Middle Devonian, where it is accompanied by Ptyc- 

 todus, Arthrodires and Crossopterygian ganoids, it takes part 

 also in the somewhat similar and nearly contemporaneous as- 

 semblage found in the Eifel District, in Rhenish Prussia. The 

 single mandibular plate represented in Plate II, Fig. 10 of the 

 present work was derived from the Middle Devonian of Bern- 



