26 NORTH AMERICAN INDEX FOSSILS. 



were distributed widely by currents as pseudo-plankton, and that 

 they hence may have come to rest where the animal never could 

 have lived. This would account well for their wide distribution 

 and excellent service as index fossils. The modern Dibranchiate 

 Spirula is known to be widely distributed in this way and Clarke 

 has shown that some Palaeozoic Ammonoids were distributed in 

 a similar manner. 



LITERATURE. 

 A. General. 

 1884. Hyatt, Alpheus. Genera of Fossil Cephalopods. Proceed- 

 ings Boston Society of Natural History, Vol. XXIL, pp. 253—338. 

 1894. Hyatt, Alpheus. Phylogeny of an Acquired Characteristic. 

 Proc. Amer. Philos. Soc, Vol. XXXII. , No. 143. 



B. Pal(Bozoic Species. 

 1879. Hall, James. Palaeontology of New York, Vol. V., Pt, II. 

 1888. Hall, James, and Clarke, J. M. Pal. N. Y., Vol. VIL, 



Supplement. 

 1890-92. Hyatt, A. Carboniferous Cephalopods. I., 2d Ann. 



Report Geol. Surv. Texas; II., ibid., 4th Ann. Rep. 

 1899. Clarke, J. M. The Naples Fauna in Western New York, Pt. 



I. i6th Ann. Rept. N. Y. State Geol., pp. 29-161, pis. 1-9. 

 1897. Clarke, J. M. The Lower Silurian [Ordovicic] Cephalopods 



of Minnesota. Pal. Minnesota, Pt. II., pp. 761-812, pis. 48-54. 

 1903. Smith, James Perrin. Carboniferous Ammonoids of Amer- 

 ica. Monograph XLII. of the U. S. Geol. Survey. — With bibU- 

 ography of works on American late Palaeozoic Ammonoids. 

 1906. Ruedemann, R. Cephalopoda of the Beekmantown and Chazy 

 Formations of the Champlain Basin. Bull. 90, N. Y. State Museum. 

 For descriptions of American Palaeozoic species, see further : the publi- 

 cations of the Canadian Survey, especially Billings, etc.. Palaeozoic 

 Fossils. — The early volumes of the Palaeontology of New York (I., 

 II. and III.) and several of the Regents' Reports, especially the 20th. — 

 The Geological Reports of the Illinois Survey, and certain ones of the 

 Indiana and the Wisconsin Survey. — Pal. New Jersey, III. (Weller) and 

 various papers by Billings, Clarke, Hall, Hyatt, Marcou, S. A. Miller, 

 Ruedemann, Shumard, J. P. Smith, Weller, C. A. White, Whiteaves, 

 Whitfield and others. 



C. Mesozoic and Cenozoic Species. 

 1852. Roemer, Ferd. Die Kreidebildung von Texas, etc. 

 1902. Anderson, Frank M. Cretaceous Deposits of the Pacific 

 Coast. Proc. Cal. Acad, of Sciences, 3d ser.. Vol. 11. , No. i. 



