DEVONIAN FISHES OF IOWA 143 



as dermal defenses of Ptyctodonts, partly on account of their 

 being a frequent accompaniment of Rhynchodus and Palseomylus 

 in the Corniferous and Hamilton respectively of Ohio and Wis- 

 consin, and partly because their triangular cross-section and seg- 

 mented structure suggest comparison with modern Chimaeroids 

 more readily than with other forms. The comparison becomes 

 effective only in so far as the anterior segment of the fossil 

 forms is brought into relation with the supporting cartilage 

 of the single dorsal fin-spine in modern Chimaeroids.* 



Formation and locality. Onondaga limestone (Ulsterian) 

 near Buffalo and Le Roy, New York, and Columbus and Dela- 

 ware limestones ("Corniferous") of Ohio. Fragmentary re- 

 mains either of this or a very similar form occur in the Ham- 

 ilton limestone (Erian) of Milwaukee, Wisconsin, and one near- 

 ly perfect specimen, now preserved in the State Museum at 

 Albany, is interesting for having been derived from the Ithaca 

 beds (recurrent Meso-Devonic fauna in the Portage) near Trux- 

 ton Corners, Cortland county, New York. 



Genus PHLYCTAENACANTHUS Eastman. 



Distinctly segmented arcuate spines of large size, with flat- 

 tened lateral faces which meet at an acute angle in front along 

 the line of insertion, and diverge outwardly and downwardly 

 on either side toward the proximal, inserted extremity, so that 

 the basal pirtion is triangular or even sitbpyramidal in outline. 

 Relations of the two segments and their general form very simi- 

 lar to those of Acantholepis, and manner of their insertion re- 

 calling the corresponding portion of Stethacanthus. 



Phlyctaenacanthus telieri Eastman. 



1898. Phlyctaenacanthus telieri C. R. Eastman, Amer. Nat. 32, p. 551, text- 



fig. 49. 



1899. Phlyctaenacanthus telieri C. R. Eastman Journ. Geol. 7, p. 283. 



1906. Phlyctaenacanthus telieri E. E. Teller, Bull. Wisconsin Nat. Hist. Soc. 



4, p. 162, pi. 1-5. 



1907. Phlyctaenacanthus telieri C. R. Eastman, Mem. N. Y. State Mus. 10, 



p. 80. 



*The mode of attachment of the dorsal fin-spine and condition of the axis in 

 Rhinochimaera and Callorhynchus of existing seas is well shown by S. Garman in 

 Bull. Mus. Comp. Zool. 1904, 41, no. 2, plates 1 and 2. 



