ICHTHYODORULITES. 
125 
1860. Haplacanihus tenuisulccctus, E. von Eichwald, Letli. Eossica, 
vol. i. p. 1599, pi. lvii. fig. 19. 
The type species.. . ^ -JVi A 
Form. &f Loct \Devonian : near St. Petersburg. -- 
A 
P. 2252. Fragment of spine. Egerton Coll. 
Genus HETSRACANTHUS, Newberry. f 7f j 
[Palseoz. Fishes N. America (Mon. U. S. Geol. Surv. no. xvi. 
1889), p. 65.] 
Spines small or of moderate size, much laterally compressed, broad 
and triangular, and gently arched; internal cavity very large, 
opening by a long fissure at the convex border; base of insertion 
short or absent. Sides of exserted portion ornamented with broad, 
flattened, smooth, longitudinal ridges, bifurcating and intercalated 
towards the base; the ridges having finely crenulated margins, 
separated by very narrow, fissure-like sulci. 
Heter acanthus politus^ Newberry. 
1889. Heter acanthus politus, J. S. Newberry, tom. cit. p. 66, pi. xxi. 
figs. 4, 5. 
Type. Columbia College, New York. 
The type species, not represented in the Collection. 
Form. Sf Log. Hamilton Group (Upper Devonian) : Milwaukee, 
Wisconsin. 
Hetera^anthus heterogyrus (Agassiz). 
[Plate III. fig. 6.] 
1845. Onchus heterogyrus, L. Agassiz, Poiss. Foss. V. G. E. p. 117, 
pi. xxxiii. figs. 16-18. 
Type. Unknown. 
This species is assigned to Heteracanthus on account of the 
characters of the superficial ornamentation. Both the type specimen 
and the example recorded below appear to be fragmentary, thus not 
exhibiting the original form of the spine. 
Form. Sf Log. Devonian: N.W. Eussia. 
P. 2248. Fragment of spine, partly shown, of twice the natural 
size, in PI. III. fig. 6. The ornament is precisely similar 
to that of the type species, which the writer has examined 
at Columbia College. Egerton Coll. 
