536 



C. R. EASTMAN 



Fig. ia. — Shag- 

 reen granules of A. 

 marshi. X f > 



brief descriptions are given of two species of Aca?ithodes, and one 

 each of Ccelacanthus and Elonichthys, with a list of the known ver- 

 tebrate fauna occurring at this locality. 



GENUS ACANTHODES, AGASSIZ. 



Representatives of the Acanthodii are extremely rare in the 

 Palaeozoic rocks of North America. If we neglect the detached 



spines of Maclicsra- 

 canthus, and the in- 

 determinable mass 

 of scales described 

 by J. M. Clarke as 

 Acanthodes pristis, 1 

 American Acan- 

 thodians are limited 

 to but three species 

 of Acanthodes and 

 one of Mesacanthus. 

 Of these Acan- 

 tliodesconcimms Whiteaves and Mesa- 

 canthus affinis (Whiteaves) occur in 

 the Upper Devonian of Scaumenac 

 Bay, Canada, and the recently de- 

 scribed Acanthodes marshi and A 

 beecheri are from the Mazon Creek 

 locality, in Illinois. 



Acanthodes marshi Eastman. 

 Fig. i. — Acanthodes marshi -n • • • „ 1 „ui~ f~« 



„ , ,, This species is remarkable tor 



Eastm. Coal-measures, Mazon L 



Creek, 111. Pectoral fin with being one of the largest, as, on the 

 associated actiontrichia and fin- other hand, A. beecheri is one of the 

 spine, xf. smallest known Acanthodians. In A. 



marshi, not only are the shagreen granules much coarser than 

 those of A. brofini and A. wardi, which are the largest of 

 European species, but the fin-spines are considerably longer 

 and stouter, averaging about o, cm long, and from .5 to .8 cm 

 z Bull. U. S. Geo/. Surv., No. 16 (1885), p. 42. 



