374 Reports and Proceedings— 



been referred to that Genus." ^ By E. Tulley Newton, Esq., E.G.S., 

 of H.M. Geological Survey. 



In this paper the author gives an account of those species of fossil 

 fishes from American and British Cretaceous strata which have been 

 referred to the genus Saurocephalns, originally founded by Harlan 

 in 1830, and regarded by him as showing Eeptilian affinities. The 

 ichthyic nature of the species first described, S. lanciformis, Harl., 

 ■was demonstrated by Prof. Owen. By Agassiz and Dixon certain 

 large fossil teeth from the White Chalk of Lewes were identified 

 with Saurocephalns lanciformis; and the latter also figures an elon- 

 gated rostrum as belonging to this fish. Dr. Leidy, in 1856, re- 

 described the original specimen of Saurocephalns lanciformis, and 

 maintained that the jaws and teeth figured by Dixon do not belong 

 to the genus Saurocephalns ; he proposed for them the new name of 

 Protosphyrcena ferox. He thought also that the rostrum figured by 

 Dixon belonged to a Sword-fish, and named the species Xiplnas 

 Dixoni. Specimens since obtained by Prof. Cope in America have 

 proved that the rostrum and teeth actually belonged to the same 

 fish, for the reception of which and of some American species Prof. 

 Cope established the genus Erisichthe. The author maintains that 

 Dr. Leidy's name, Protosphyrcena, must be adopted for this genus, 

 which will include the British Protosphyrcena ferox (= Erisichthe 

 Dixoni, Cope) and the American species, P. angulata, anitida, pene- 

 trans, and ziphioides (Cope). The characters of these species are 

 discussed by the author. The species known on the Continent as 

 Saurocephalns alhensis and influens, Pict. et Camp., S. dispar, Heb., 

 and S. incequalis and substriatus, Miinst., are founded on isolated 

 teeth, and their affinities are regarded by the author as doubtful. 

 Saurodon Leanus, Hayes, from the Greensand of New Jersey, belongs 

 to Saurocephalns, which also includes a species described by Prof. 

 Cope iinder the name of S. arapahoviiis. Teeth erroneously referred 

 by Agassiz to Saurodon Leanus were regarded by Dr. Leidy as re- 

 presenting a new genus and species, Cimolichthys levesiensis, and to 

 this last-named genus the author refers Spinax marginatus, Reuss, 

 and, doubtfully, Saurocephalns striatus, Ag. 



5. " A Microscopical Study of some Huronian Clay-slates." By 

 Dr. Arthur Wichmann. 



Although a considerable amount of attention has been devoted 

 during recent years to the microscopical study of clay-slates and 

 slate-clays, yet in none of the published researches on this subject 

 has any account of the structure of the clay-slates of Archtean age 

 been given. The author has availed himself of the extensive series 

 of Huronian clay-slates collected by Major T. V. Brooks in the 

 country around Lake Superior to supply this deficiency. The suc- 

 cession and relation of the rocks described have been fully treated 

 of in the work of Hermann Credner and the publications of the 

 Geological Survey of Michigan. 



The chief object of the author is to discuss the origin of the crys- 



1 On this genus see a paper by Mr. W. Davies, F.G.S., in the Geol. Mag. 1878, 

 for June last, p. 254, PI. VIII. 



