﻿ICHTHYODORTJLITES. 149 



denticles of the concave margin appear to be directly con- 

 tinuous with the lateral ribs. 



Presented by Prof. L. G. de KonincJc, 1876. 



The following species have also been described : — 



Listracanihus beyriehi, A. von Koenen, Neues Jahrb. 1879, 

 p. 341, pi. vii. fig. 1 : Pamphr actus hydrqphilus, H. Hey- 



marm (errore), Sitzungsb. niederrhein. Gesell. 1870, 

 p. 217. — Culm-Measures ; Herborn, Nassau. 

 Listracanihus hildrethi, J. S. Newberry, Eep. Geol. Surv. Ohio, 

 vol. ii. pt. ii. (1875). p. 56, pi. lix. fig. 6. — Carboniferous; 

 Ohio. [Marietta College, Ohio.] 



A species of this genus from the Calciferous Sandstones of East 

 Kilbride, Lanarkshire, is also preserved in the collection of Dr. 

 John Hunter, Braidwood, near Carluke. 



Genus BYSSACANTHUS, Agassiz. 

 [Poiss. Foss. Vieux Gres Rouge, 1845, pp. Ill, 116.] 



Basal portion of spine broad, not deeply inserted, with a large 

 central eavit} T , tapering above and passing into a cylindrical elon- 

 gated portion, straight or slightly arched, with a blunt apex. The 

 surface of the cylindrical portion ornamented with coarse longitu- 

 dinal ridges, diverging and fewer upon the broad basal portion. 



Byssacanthus crenulatus, Agassiz. 



1845. Byssacanthus crenulatus, L. Agassiz, op. cit. pp. Ill, 116, 



pi. xxxiii. figs. 11-14. 

 1860. Byssacanthus crenulatus, E. von Eichwald, Leth. Rossica, vol. i. 



p. 1598. 



Type. Keyserling Collection. 



The type species. 



Form, fy Loc. Devonian : St. Petersburg, Russia. 



P. 2251. Two fragments. Egerton Coll. 



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

 examples in the Collection : — 



Byssacanthus arcuatus, L. Agassiz, Poiss. Foss. V. G. R. (1845), 

 p. Ill : Onchus arcuatus, L. Agassiz, Poiss. Foss. vol. iii. 



