﻿ICHTHYODORULTTES. 



Ill 



The following species have also been described, but there are no 

 examples in the Collection :— 



Aster optychius bellulus, St. John & Worthen, Pal. Illinois, vol. vi. 



(1875), p. 439, pi. xvi. fig. 7. — Coal-Measures ; Illinois 



and Iowa. 

 Aster optychius elecjans, J. S. Newberry, Palaeoz. Fishes N. America 



(Mon. U.S. Geol. Surv. no. xvi. 1889), p. 176, pi. xxv. 



fig. 4. — "Waverly Group (Lower Carboniferous); Michigan. 



[Columbia College, New York.] 

 Aster optychius sancti-ludovici, St. John & Worthen, op. cit. vol. vi. 



p. 437, pi. xvi. figs. 3. 4. — St. Louis Limestone; Illinois 



and Missouri. 

 Aster optychius triangularis, Newberry & Worthen, Pal. Illinois, 



vol. iv. (1870), p. 370, pi. ii. fig. 4. — Burlington Lime- 

 stone; Illinois. 



Four doubtful, fragmentary spines are also named Aster optychius 

 Iceokulc, St. John & Worthen (op. cit. vol. vi. p. 436, pi. xvi. fig. 2), 

 from the Keokuk Limestone of Illinois ; A. tenellus, St. John & 

 Worthen (op. cit. vol. vii. p. 248, pi. xxi. fig. 4), from the Upper 

 Coal-Measures of Kansas ; A. ? tenuis, St. John & Worthen (op. cit. 

 vol. vi. p. 438, pi. xvi. figs. 5, 6), from the Chester Limestone of 

 Illinois ; and A. vetustus, St. John & Worthen (op. cit. vol. vi. p. 435, 

 pi. xvi. fig. 1), from the Kinderhook Limestone of Iowa. 



Genus COSMACANTHUS, Agassiz. 

 [Poiss. Foss. Vieux Gres Eouge, 1845, p. 120.] 



Syn. Geisacanthus, St. John & Worthen, Pal. Illinois, vol. vi. (1875), 

 p. 440. 



Dorsal fin-spines of small size, slender, more or less laterally com- 

 pressed and very slightly arched ; sides of exserted portion orna- 

 mented with longitudinal series of ganoine-coated tubercles, and the 

 anterior margin often keeled ; posterior face flat or concave, without 

 lateral denticles, but sometimes with a median keel. 



The type species of this genus (0. malcolmsoni) is regarded by 

 Pander 1 as founded upon a fragment of Placoderm armour ; and if 

 this re-determination prove correct, the Carboniferous Ichthyodoru- 

 lites recorded below must be named Geisacanthus. 



1 C. H. Pander, Placoderm. devon. Syst. 1857, p. 18. 



