NO. 2177. FOSSIL FISHES IN NATIONAL MUSEUM— EASTMAN. 237 



Influenced by the idea that some of the tubercidated dermal plates 

 described by Doctor Walcott from the Canon City locality bore a 

 strong resemblance to certain well-known Devonian fishes, such as 

 Coccosteus and Asterolepids, the suggestion has been put forward by 

 some writers that the fish beds at Canon City are probably not of 

 Ordovician but of Devonian age. The suggestion appears untenable 

 in view of the fact that the accompanying invertebrate fauna, repre- 

 sented by more than thirty species, exhibits clearly the facies of the 

 Middle Ordovician limestone of New York and the Mississippi Valley. 

 The same invertebrate fauna persists upward to a horizon 180 feet 

 above the fish beds, and includes a number of highly characteristic 

 fonns, such as ReceptacuUtcs oweni and various molluscous and crus- 

 tacean species. An excellent account of this and the corresponding 

 section in Wyoming was published by N. H. Darton ^ in 1907, and 

 two years later the same author ^ announced the discovery of fish 

 remains in the Ordovician near Rapid City, South Dakota. 



Still more recently, in 1913, the discovery was announced by T. D. 

 A. Cockerell ^ of another locaHty in Colorado, near Oliio City, at 

 which fish-remains occur similar to those found at Canon City, and 

 accompanied by the same invertebrate fauna. Professor Cockerell 

 is impressed by the extraordianry resemblance that the fish remains 

 from the Ohio City locaUty bear to well-known types of Devonian 

 fishes, and claims to have found representatives of three famihes, 

 Diplacanthidae, Holoptychiidae, and Coccosteidae. These deter- 

 minations are admitted, however, to be merely approximate, and can 

 only be accepted in a provisional sense until the material has been 

 carefully investigated. The Ordovician age of the containing beds 

 seems to bo conclusively estabUshed by the evidence of invertebrate 

 remains. 



OSTRACODERMI. 



ASTRASPIDAE, new family. 



An imperfectly definable family, known only by a single genus, 

 Astraspis, which has the large median dorsal and ventral plates of 

 the body armor constructed in the same fashion as in the Psammos- 

 teidae, out of fused polygonal tesserae, and the external ornament 

 of these plates also similar in a general way to that observed in var- 

 ious genera of Heterostracous Ostracoderms. 



1 Ordovician of the Bighorn Mountains. Bull. Geol. Soc. Amer., vol. 17, 1907, pp. 541-566. 



2 Discovery of fch remains in the Ordovician of the Black Hills, South Dakota. Bull. Geol. Soc. Amer., 

 vol. 19, 1909, pp. 567-568. 



' Cockerell, T. D. A. Ordovician (7) fish remains in Colorado. Amer. Naturalist, vol. 47, 1913, pp. 246- 

 247. 



