DEVONIAN FISHES OF IOWA 145 



thaspis and certain very similar structures that have been de- 

 scribed by Jaekel in natural association with the dentition and 

 other parts of the skeleton of "Rhanrphodus", a name which we 

 have shown to be synonymous with Rhynchodus. Attention has 

 also been called to the fact that plates of almost identical con- 

 formation, and without doubt of the same nature as the dermal 

 ossifications described by Jaekel, are an invariable accompani- 

 ment of Rhynchodus excavatus in the Middle Devonian of Iowa 

 and Wisconsin. A like coincidence is to be noted in the distri- 

 bution of the so-called Acanthaspis armata and the type species 

 of Rhynchodus (R. secans) ; and as regards the two or three 

 Eifelian species of Rhynchodus, these, are accompanied by the 

 dissociated spiniferous bodies known as Acanthaspis pruemensis 

 Traquair* and A. tuberculatus Eastman.f On the other hand, 

 the peculiar Asterolepid described by Smith Woodwardi: from 

 the Lower Devonian of Spitzbergen, and characterized by having 

 a fixed spinous appendage, must be regarded as of totally differ- 

 ent nature, whose distinctness from either Phlyctaenaspis- or 

 "Acanthaspis "-like forms is best indicated by making it the 

 type of an independent genus. For this the name of Akctolepis 

 is proposed, in allusion to its hyperborean habitat. Besides the 

 type species, A. decipiens (Woodward), it is possible that a sec- 

 ond Spitzbergen species, described by Smith Woodward under 

 the name of Acanthaspis minor, should also be referred to the 

 same genus. The correctness of Woodward's reference of these 

 forms to the Asterolepidae apparently admits of no question. 



Acanthaspis armata Newberry. 

 (Plate I, Fig. 14) 



1875. Acanthaspis armatus J. S. Newberry, Eept. Geol. Surv. Ohio, Pal. 2, 



pt. 2, p. 37, pi. 53, figs. 1-6. 

 1889. Acanthaspis armatus J . S. Newberry, Monogr. U. S. Geol. Surv. 16, p. 



36, pi. 31. 

 1894. Acanthaspis armata R. H. Traquair, Ann. Mag. Nat. Hist. ser. 6, 14, 



p. 371. 



* Traquair, E. H., Notes on Palaeozoic Fishes. Ann. Mag. Nat. Hist. 1894, ser. 

 6, 14,- p. 370. 



t Eastman, C. R., Devonische Fischreste aus der Eifel. Centralblatt fur Mineral. 

 1900, p. 178. Also in Amer. Geol. 1900, 25, p. 392. Original figured by 

 F. Roemer, Lethsea Geognostica, 1876, 1, pi. 31, fig. 10. 



t Woodward, A. S., The Devonian Fish-Fauna of Spitzbergen. Ann. Mag. Nat. 

 Hist. 1891, ser. 6, 8, p. 4, pi. 1. 

 10 



