DEVONIAN FISHES OF IOWA 113 



discovery of complete skeletons of Gyracaiitliides, from the Car- 

 boniferous of Australia, the Acanthodian nature of the Gyra- 

 canthus type of fin-spines has been positively established within 

 the past year or two.* 



Acanthodes (?) pristis Clarke. 



1885. Acanthodes ? pristis J. M. Clarke, Bull. U. S. Geol. Surv., no. 16, p. 42. 

 1891. Acanthodes 1 pristis A. S. Woodward, Cat. Foss. Fishes Brit. Mus. pt. 2, 



p. 15. 

 1902. Acanthoessus ? pristis 0. P. Hay, Bull. U. S. Geol. Surv., no. 179, 



p. 273. 

 1907. Acanthodes f pristis C. R. Eastman, Mem. N. Y. State Mus. 10, p. 64. 



Founded upon a considerable portion of the shagreen of an 

 undoubted Acanthodian fish, the family position of which, owing 

 to non-preservation of the fins, is uncertain. In the solitary 

 known specimen, the greater number of scales have retained their 

 natural exceedingly compact arrangement, and are so minute 

 as to indicate a species of very diminutive proportions. Their 

 characters are given in the original description as follows: 



"The scales are very small, measuring .5 mm on the edge, 

 square or slightly sub-rhomboidal in outline, and one-fourth as 

 thick as wide. The adjacent edges at about two-thirds the dis- 

 tance from the upper surface are strongly grooved by a single 

 deep furrow. The upper surface of the scales is smooth and 

 slightly convex. ' ' 



Formation and locality. Ehinestreet shale of the Portage 

 beds ; near Sparta, New York. 



Genus machaebacanthus Newberry. 



Spines, so far as known, elongated, tapering, more or less 

 curved and somewhat laterally compressed, with sharp edges 

 and a very large longitudinal ridge on each side ; central cavity 

 extending nearly to the apex; external surface covered with a 

 thin layer of ganodentine, smooth, finely punctate, or sometimes 

 longitudinally striated. 



* Woodward, A. S., On a Carboniferous Fish-fauna from the Mansfield District, 

 Victoria. Mem. Nat. Mus. Melbourne, 1906, 1, pp. 1-32. See also Bashford Dean's 

 recent paper: Notes on Acanthodian Sharks. Amer. Journ. Anat. 1907, 7, pp. 

 209-222. 



