366 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



specimens. Dr. Owen's species, D. granulosus and D. miniscaensis. 

 were placed in the genus Ptychaspis, and D. ioivensis under Cono- 

 cephalites. 



In a review of Hall's work of 1863 in the American Journal of 

 Science and Arts, the writer (probably James D. Dana) calls attention 

 to the spelling of the name Dikelocephalus and states that the true 

 orthography is Diccllocephahis. 



In 1866 Mr. J. W. Salter gave a very brief interpretation of Dikelo- 

 cephalus and referred four species to it: Dikelocephalus (Centro- 

 pleiira ?) fiirca {^= Dikelokephalina Brogger ??), Dikelocephalus 

 celticns (= Distorted pygidia, genus ?), D. ? {Centropleura ?) dis- 

 cordalus (= Perhaps Anomocare ?), D. ? ( Centropleum f) sp. 

 (= Anomocare ?). 



Messrs. Hall and Whitfield (1877) mention the genus in connec- 

 tion with the reference of two forms of pygidium of three species to it. 

 The first, D. bilobatus, has the generic name Pterocephalus bracketed 

 with it in the description of the plate, but it is probably a species of 

 Anomocare. The other two species, D. multicinctus and D. Hahellifcr 

 may be referred to Apatokephalus ? {=^ Brogger, 1897). 



In 1878 Prof. R. P. Whitfield noted the occurrence of specimens 

 of trilobites preserving their natural convexity that he referred to 

 " Dikellocephalus," as D. harabucnsis ( = Platycolpus) and D. eatoni 

 ( =z Platycolpus) . This matter was reprinted in 1882 with illustra- 

 tions of the species. 



Dr. W. Dames (1883, pp. 5, 6) calls attention to the confusion 

 existing among the species referred to " Dikellocephalus " and sug- 

 gests the establishing of a new genus for Owen's D. pepinensis. He 

 comments favorably on Hall's references, but calls attention to the less 

 careful work of Billings. 



Dr. G. F. Matthew (1893) attempted in a general manner to 

 discuss the value of the generic reference of the many species that 

 had been placed under Dikelocephalus by authors and to draw con- 

 clusions on the supposed stratigraphic position of the genus. He 

 concluded that in America it was strictly a Cambrian genus, and in 

 Europe Ordovician. 



In 1896 Dr. Brogger followed up a previous suggestion that he 

 had made and placed several species that had been referred to Dikelo- 

 cephalus under the new genera Dikelokephalina, Conokephalina, and 

 Apatokephalus. 



Dr. Beecher (1897) constituted the subfamily Dikelocephalinse to 

 include Dikelocephalus and allied genera. 



