﻿146 1CHTHY0D0RULITES. 



ornament or layer of ganoine ; an unsymmetrical double longi- 

 tudinal series of denticles on the posterior aspect distally. 



This genus is not represented in the Collection, and is known 

 only by the type species : — 



Aganacanthus striahdus, R. H. Traquair, he. cit. p. 64. — Middle 

 Carboniferous Limestone (Blackband Ironstone) : Borough 

 Lee, near Edinburgh. [Collection of Dr. R. H. Traquair.] 



Probably to this group of Ichthyodorulites may also be assigned 

 the following genus and species : — 



Gomphacanthus acutus, J. W. Davis, Quart. Journ. Geol. Soc. 

 vol. xl. (1884), p. 618, pi. xxvi. fig. 9.— Lower Carboni- 

 ferous (Yoredale Rocks) ; Wensleydale, Yorkshire. [York 

 Museum.] 



IY. Spines probably not placed in advance of fins, but most nearly 

 resembling the head-spines of the male Chimaeroids and some 

 Mesozoic Cestraciont Sharks (e. g. Hybodus). 



Genus ERISMACANTHUS, M'Coy. 

 [Ann. Mag. Nat. Hist. [2] vol. ii. 1848, p. 118.] 



Syn. Cladacanthus, J. W. Davis (ex Agassiz, MS.), Trans. Roy. Dublin 

 Soc. [2] vol. i. 1883, p. 364. 



Basal portion of spine broad, laterally compressed, not deeply 

 inserted, soon bifurcating above into two slender divergent branches 

 in the same vertical plane ; one branch considerably arched, keeled, 

 and pointed distally, with a series of denticles upon the concave 

 margin ; the other branch longer, not tapering to a point, but ter- 

 minating in a cluster of elongated tubercles. An internal cavity 

 extending throughout the spine. Superficial ornament of exserted 

 portion consisting o£ tubercles and sulcations, the latter predomi- 

 nating in the short pointed branch of the spine. 



Erismacanthus jonesi, M'Coy. 



1843. Cladacanthus paradoxus, L. Agassiz, Poiss. Foss. vol. iii. p. 176 



(name only). 

 1848. Erismacanthus jonesii, F. M'Coy, Ann. Mag. Nat. Hist. [2] 



vol. ii. p. 119. 

 1848. Dipriacanthus falcatus, F. M'Coy, ibid. p. 121. [Mus. Geol. 



Soc. London.] 



